It has been just over two years since Apple last revamped the iMac's design, and the refinements are largely worth it. The new iMac now comes in three processor flavors and two screen options. The stock processor options are either the 3.06GHz Intel Core 2 Duo (the same processor offered in the last-generation iMacs, but with faster configurations) or a 2.66GHz Intel Core i5 (the first quad-core option to come to the iMac), and you can get a 2.8GHz Intel Core i7 as a build-to-order option. For the display, the 21" iMac has now morphed into the 21.5" (to accommodate a 16:9 aspect ratio), and the high-end option is now 27".

For this review, we looked at the 3.06GHz Core 2 Duo 27" iMac model, as we felt it has the most universal appeal to those looking to buy an iMac.

3.06GHz Intel Core 2 Duo
2560 x 1440
4GB RAM
1TB hard drive
8x SuperDrive
ATI Radeon 4670 with 256MB
$1,699

In the box

Aside from the iMac itself, the new machines come packed with an Apple Wireless Keyboard and a new Magic Mouse (read our review of the Magic Mouse here). The wireless keyboard is the same as what Apple has been offering for some time now, though the new new keyboard now requires only two batteries, instead of the three required in the old one. How green.

Screen

The aluminum and glass design is here to stay, but gone is the border around the display—allowing the colors on the screen to truly pop—and the screen is now a true 16:9 aspect ratio. In the photo below, you can see the 2009 27" iMac next to a 2007-era 24" iMac:

This is by far the largest screen that Apple has put on one of its machines, and we love it. The highest resolution it can handle is 2560 x 1440, and the aspect ratio change shows that Apple is aware that people are using these machines more and more as devices to watch HD movies, and not just for your standard computing purposes.

More important than the screen size itself is the fact that the new displays are finally LED-backlit like the rest of Apple's notebooks and cinema displays. Again, this is the first time Apple has added LED backlighting to the iMac, allowing the screen to go both brighter and dimmer than the previous generation. For a headache-prone, light-sensitive user like myself, the ability to dim the screen to my satisfaction is a blessing—the lowest possible brightness setting on my 24" iMac was too bright for me. The 27" iMac's equivalent brightness setting is somewhere in the middle, meaning that I can go even lower if I'm having a particularly headache-y day. Thank you, Apple.

Frankly, there isn't a ton to say about the new display except that it's bigger, brighter (or dimmer), and just as nice to look at as the previous models. It offers the same level of contrasty goodness that most customers have come to expect from current Apple products, though the glossiness remains, which could still be an annoying sticking point for some old greybearded users. (We, however, have come to accept it.)

Bonus external monitor included! (Some restrictions may apply)

One of the selling points of the new iMac is not just that it has a gigantic, pretty monitor for its own use—the 27" version can also be used as an external display for supported other devices (sorry, but the 21.5" iMac is left out on this feature). What does this mean? Like the rest of Apple's Mac offerings, the iMac has a Mini DisplayPort for video output, which can be used with a variety of third-party monitors (usually with the help of an adapter) or Apple's own Cinema Display. However, this particular Mini DisplayPort can also take input from another Mini DisplayPort connection.

So, if you have a MacBook Pro that also has Mini DisplayPort-out, you can connect it to your 2009 iMac with a Mini DisplayPort to Mini DisplayPort cable (Belkin sells one through the Apple Store for $29.95, as does Monoprice at $5.81 for a 6-foot cable). This will allow you to use your MacBook Pro with your giant iMac display instead of its comparatively tiny built-in screen.

This sounds cool on the surface, and it is. However, there are several questions as to why one would want to do this. Theoretically, if you own both a MacBook Pro and an iMac and you currently have access to both, why would you bother to do the work on the MacBook Pro if you need the screen size of the iMac? (Basically, just use the iMac.)

Or, if you prefer your MacBook Pro for power or data purposes, why do you even have an iMac in the first place when you could have spent less on an external Cinema Display (or some other, cheaper monitor)? Still, it's a nice feature to have, and certainly an option for the future when your 2009 iMac becomes old and decrepit and you stop using it for anything besides its display. In this case, the display certainly can continue to be useful for far longer than the computer inside.

For kicks, we decided to test this with a new 13" MacBook Pro using the Mini DisplayPort-to-Mini DisplayPort cable from Monoprice. When you connect both ends of the cable to a computer, the iMac's screen automatically switches over and acts as a secondary monitor for the computer you just plugged in—there's no fussing with settings required. By default, the iMac acts as a display set to the left of your notebook, but through System Preferences > Displays, you can change that to be whatever configuration you want. Unplugging the cable will automatically return the iMac to its normal state.

The major downside to this feature is that it's limited to devices that have DisplayPort output. This means that, for the time being, you're pretty much limited to connecting other Macs to your 27" iMac. Grand dreams of connecting an Xbox 360 (something Gaming Editor Ben Kuchera was dying to do) or a Blu-ray player are not entirely dashed—it could be possible one day if a Blu-ray player or console maker decides to put DisplayPort out on one of their devices—but it's currently impossible for the time being. No number of adapters will help; it has to be DisplayPort-out or bust.

Ports

The 2009 model also got a slight port rearrangement and a couple of port replacements compared to the 2007 model that we compared it to (but it should be noted that the iMac revision from March of 2009 had the same collection of ports as the current 27" iMac does).

Gone is FireWire 400 in favor of one extra USB 2.0 port (for a total of four instead of three). FireWire 800 remains for video enthusiasts, and the mini-DVI port is now Mini DisplayPort. The extra USB port is a welcome change, though I found myself annoyed that I must purchase yet another adapter so I can use my external monitor with my iMac—something I have had to do with every single one of the last four iMacs I've owned. (Luckily, a VGA-to-Mini DisplayPort adapter exists, as well as an HDMI-to-Mini DisplayPort.)

Apple has also pushed the iMac in the footsteps of its notebook line by adding an SD card slot right in the machine. Located on the right-hand side just below the SuperDrive, the SD card slot is easy to miss, but it's convenient addition for those who don't like taking up an extra USB port with annoying and unsightly camera cables. We can't say this is a major factor in deciding to buy a new iMac, but it's at least handy to have. I've used it a few times already, and you can set iPhoto or Aperture to start when you insert the card just like you would if you were connecting a camera.

Performance

Regular use of the 27" iMac is about what one might expect from a 3.06GHz Core 2 Duo machine. At this point in consumer-level machines, speed bumps make less of a difference in day-to-day life, although the stock 4GB of RAM is a nice starting point, as is the 7200rpm hard drive.

One odd bump that several of us at Ars noticed in our stock 27" iMac configurations (which came with Mac OS X 10.6.1) was that Flash videos seemed jerky to the point of being borderline unwatchable. From personal experience, it was akin to watching YouTube videos on a first-generation MacBook Air—not something you want to do if you can avoid it. Flash isn't exactly known for being snappy on the Mac in general, but this was a strange development given the hardware in the 2009 iMac. Running a software update to 10.6.2 and the latest version of Safari fixed the problem, however.

For those who like numbers, we ran our typical Xbench and Cinebench benchmarks on the latest iMac as well. However, we should note that since this machine isn't the new i5 or i7 from Intel, the results are not entirely unexpected—it's basically the same processor as the previous-gen iMac, but faster. Given this consideration, we didn't go the whole hog just to take up page space. Here are the basics:

Xbench 1.3 and Cinebench 10

iMac 27"

3.06GHz Core 2 Duo CPU
4GB of RAM
7200rpm 1TB SATA HD
ATI Radeon HD 4670 graphics

iMac 20"

2.4GHz Core 2 Duo CPU
1GB of RAM
7200rpm 320GB SATA HD
ATI Radeon 2600 PRO graphics

MacBook Pro

2.4GHz Core 2 Duo CPU
1GB of RAM
5400rpm 160GB SATA HD
NVIDIA GeForce 8600M GT graphics

It's unsurprising to see the 27" iMac do well in most of these tests. Not only does the 27" iMac have a faster version of the same processor than the other machines tested, it also has an improved graphics card from ATI. We're not sure why the 27" iMac fared worse than the 20" iMac in Xbench's disk test, however—they both have the same speed hard drives—and the user interface test is also perplexing. We ran our benchmarks twice just to be sure and came out with about the same numbers.

Conclusion

If you liked the previous iMac, you'll like the new iMac—especially the 27" version. The single largest improvement is by far the screen, both in its size and its LED backlighting, which gives you tons of space for work and play on a crisp-looking display. And if you've dreamed up some scenario in which you need both an all-in-one computer and an external display for use with a notebook on the same desk, then this is practically your dream machine.

The downsides to the iMac are the same downsides that have almost always been there—while it's possible to perform some upgrades, it's an all-in-one with limitations. Still, the stock offerings are nice, and it's easy for most of us (who are not video professionals, for example) to get work done on this machine. If you still harbor hate for glossy displays, then you have likely already ditched most of Apple's offerings anyway. And if you wanted to use this thing as an external display for your gaming console, you're going to be disappointed (for the time being).

Depending on what you value most, the 27" iMac may or may not be worth the price of an upgrade. Compared to the previous-gen iMac, the non-display changes are relatively minor—under normal circumstances, I would not have paid the money to upgrade to it from my 24" iMac just yet. That doesn't mean I'm not a fan of this computer, though (in fact, I adore it); it just means if I were a typical customer, I would wait for either a more significant update or for my 24" iMac to grow a little longer in the tooth.

The good:

• Bigger screen on a desktop is almost always better
• LED backlighting means it can go brighter and dimmer than iMac predecessors
• Performance is good, about what you would expect for this configuration

The bad:

• Mini DisplayPort-in can only take input from other devices with DisplayPort-out
• Yep, the display is still painfully glossy

The ugly:

• Not very upgradeable aside from RAM