Here's a few reasons why they suck:
1) Ugly. It looks like they asked Dell's design team to make an iMac. I swear, if anybody can look at it and one of the newer Optiplex / Dimensions side by side and not say that if Dell made an All-In-One those are the colors and pattern they'd use (granted it wouldn't be rounded, or polished, or have a huge honkin apple logo front and back, but still). And which genius shipped a white-capped keyboard with a black and Al mac?
2) Display, for multiple reasons:
a) Viewing angles are horrible.
b) I'm not going to re-layout my entire room or office if the lighting is wrong.
c) ANybody wnat to use dual monitors? Any of you ever use a Glossy display side by side with a matte? Every try to calibrate them so they look even remotely close? How many people are ready to rush out and buy one of the half a dozen aftermarket LCDs that use a glossy finish (note that Apple's own Cinema's aren't on this list), and throw out existing displays, just to use duals? If i were Apple i would have tried to match them as closely as possible with the Cinemas and make a push that dual monitors increases producitivity.
d) its a laptop style panel, vs the traditional desktop style (FN vs ISP for those who care). It gives them a distinctly different picture from a desktop display, and one more nail in the coffin of why this model sucks when used with a 2nd display.
3) Graphics -- I don't care if ATI has dedicated themselves to Apple's needs, screwing over the low end guys by not even offering 256MB of graphics memory as a BTO option is just wrong, especially with Leopard and its memory-hungry CoreAnimation right aroudn teh corner. I'm sick of hearing comments on how great WoW runs on this machine, big deal, how old is that game again? How about something made in the last 6 months, let alone something more current (are there even any games out there for the Mac right now that would push those limits...). Its sad when the Macbook Pros have better graphics than the iMacs do.
4) Keyboard -- Being ugly isn't enough, waht is the deal with the function keys? Why don't they just abolish the iMac and make a 20" laptop? F9,10,11, and 12 weren't good enough for Expose and Dashboard? As was noted earlier, this wasn't successful for PCs, why does Apple doing it suddenly make it intelligent and innovative? Were their no Apps out there that used the F1-4 keys? And adding one more modifier, the fn key, great idea. We really could have used one of those located as far away from the first 8 function keys as humanly possible without putting it in the number pad, oh wait! Thats exactly where they put it!
I was psyced to buy one. Really, i was. When i first saw them, wow. Then i saw them in person. Glossy = dealbreaker, i can't use two displays with different finishes. The eyestrain alone would be unbearable, and my machine is a tool even more than it is a toy or an appliance. This means if my eyes hurt after 2 hours, i can't just stop playing my game, or browsing the internet, if i can't remain productive, writing code and scripts, testing, staring at dozens of terminal windows and a boatload of reference material, i don't make money. and if its the display thats the problem, that's a pretty big deal. So am i supposed to spend 2-3 times as much on a Mac Pro that is 5 times the size, has 10x the necessary processing power, not ot mention consumes a boatload more power when running, is noiser and can double as a space heater (not that the iMacs are blocks of dry ice...)? Are you kidding me?!
I can put up with the ugly looks, i can put up with a craptastic keyboard, and i could even put up with a laptop-display in a desktop. But i need 2 things out of my machines, RAM and screen real estate. I guess i'll just suffer along with my Mini on a 20" display and PC with dual 17s" until i either get fed up and buy an overpowered and over priced (for my purposes both are true) Mac Pro or Apple finally releases a 'Mac Semi-Pro' for those who need a workstation but not a server, or a tower the size of a small child or the heat, processing power, or options that come with it.