I laugh when people suggest using a laptop (or even a computer, more on that in a sec) as an alternative to a media center like the AppleTV, or even the (hacked) XBox or XBox360. For one, having to hook up a laptop every time you want to watch a movie would be a royal pain in the ass. (Imagine having to hook up your game console, DVD player, etc each time you'd want to watch/play it and it'd lose a lot of it's appeal, too.)
As far as the computer, maybe with the exception of Windows Media Center (depending on the computer), I believe what's made for the TV looks best on a TV and what's made for a computer looks best on the computer (monitor). Back in the day, S-video connections were way fuzzy (downrez) even on the better video-out cards. The emulator games on the XBox (hacked) through S-video looks far better than the same emulated games on a PC hooked up via the same connection. And these days, HDTV owners have to deal with overscan problems when hooking a computer up. Some computers have settings to counter this, but they can vary. I hooked up a Mac Mini to my HDTV and couldn't get it to look just right.
Lastly, devices intended for the home center first take user interface/remote into consideration. When I had the Mac Mini hooked up, I was always tethered to the mouse in "some" way when the odd situation came up that didn't involve Front Row / Apple remote.
TV is its lack of a DVD player. If it had this, it would allow people to use it as an "all in one" media center. Sure there are movies and shows on iTunes, but what if it's a DVD that isn't available via iTunes? Having a built-in DVD player probably wouldn't cost too much more on Apple's part, and it would make the high price a lot more justifiable.
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