I'd actually been planning to get one of them for a while; more precisely, I'd been planning on getting one once the Thunderbolt models were released, and here they are (well, I'd been planning on getting one before Thunderbolt was announced, but once it was announced, that became the target). Okay, somewhere in the middle there, I'd actually been planning on waiting a little bit longer, but I had a reason for getting it now, too (which I'll get to in a second).
Anyway, the primary use for the thing will be photography (editing photos and whatnot). I'd been using the laptop, which was barely standing up under the strain of editing raw images with Aperture (just not enough memory, mostly), and, well, not enough screen real-estate. Originally I'd hooked up the 30" monitor to the laptop as well, but honestly that didn't really work out. Converting mini-displayport to dual-channel DVI-D was a touchy process at best (two incompatible digital standards requires actual live circuitry to do the task), and I kinda gave up on it when I got back from Japan and moved the the 30" screen to my Windows box(es).
Anyway, besides the photography thing, I'll be using it as a remote desktop for my work computer (which is why I got it now). And, other than that, well, random stuff. Maybe some rendering -- the one I got is a real beast. Most day-to-day stuff (mail, what have you) will probably stay on the laptop, though.
But, just because it amuses me, I'm going to compare it to the game box I built in February (it's remarkably comparable):
Game machine: quad-core 3.06GHz i7-950, iMac: quad-core 3.4GHz i7-2600
This is the one component where the iMac is clearly ahead: the Sandy Bridge processor is about 40% faster than the Bloomfield chip. That said, CPU wasn't a priority on the game machine, both processors are plenty fast. But, since I was considering using the iMac for rendering as well as photography, it was a slightly bigger priority here.
Game machine: 12GB DDR3-1333, iMac: 16GB DDR3-1333
This one's probably a toss-up: since the iMac has two banks of two DIMMs vs. two banks of three DIMMs, I'm not sure it's actually using the three channels the processor and chipset support. Either way, both should have plenty. The real question is what I'm going to do with the 4GB of lower density RAM I'm taking out of the iMac.
Game machine: 1.25GB GeForce GTX 470, iMac: 1GB Radeon HD 6970M
This one, more surprisingly, is also a toss-up. The GTX 470 is only about 6% faster than the Radeon. I'm actually somewhat shocked that you can get that much performance out of a mobility card (happy, but still shocked -- on the other hand, if I was getting a new graphics card for the game machine today, it'd be about 20% faster yet). This situation, however, is sort of the opposite of the situation with the CPU -- graphics speed wasn't really a priority on the iMac, as long as it was adequate.
Game machine: 1TB 7200rpm HD + 64GB SSD, 2560x1600 30" display
iMac: 2TB 7200rpm HD (no SSD), 2560x1440 27" display
Screen size was a priority on both machines; both are fine. I'd have liked a little more vertical space on the iMac, but it's hard to actually complain about 2560x1440. Plus, the 27" iMac actually supports two external 30" monitors like I have on the game machine if I ever needed more space, but I really don't, at least not at this point (and, well, I also don't have the desk space). The SSD option (like the build-to-order memory option) was just too expensive from Apple to be remotely worth it; having enough space for photos was a bigger priority, anyway. And, unlike upgrading memory, upgrading drives yourself on the iMac is an ordeal, so I bit the bullet and just swallowed the Apple tax for the larger HD. It ought to hold me over for a few years, and even if not, Thunderbolt drives ought to be out eventually. At 10Gb/s, it's actually faster than the SATA III (6Gb/s) either box has internally.
You can look up actual prices if you like, but the short of it is, when you account for the fact that the iMac has a fairly beefy monitor built-in, it's actually more-or-less a tossup. If I'd had to have bought the monitor for the game machine, and not had to deal with Apple tax on built-to-order options -- not to mention the sales tax I had to pay on the iMac, grrr -- the iMac actually would have been the significantly cheaper option. But, it's not an entirely apples-to-Apple (*ahem*) comparison -- I do get to keep the monitor even if I retire the game box, after all (and I'm also using it for another box behind a switch). But the point is, the iMac's price isn't terrible, at least not for the high-end 27" model (considering build quality and design, I wouldn't put the Apple tax over 10%, if even that much -- and most of that is the product of idiotic build-to-order pricing).
And that'll be my new toy next week. It's going to start looking like my own personal NOC down there what with all the screen real-estate I'm acquiring.