iMac now Idon'tPC

Wow, I never realized exactly how big a 24" screen really was until it was on my desk.
Screen: Big, bright, and hi-res. Perhaps a little too bright however. And it doesn't seem to be as adjustable as I'd like. Even at its dimmest setting, it seems a little too bright. Having lots of screen real estate makes being productive that much easier. I can have several windows open at the same time, and get the data I need to compile it in another without having to switch; however, even if I did have to switch, OS X makes that easy too (but this is a review of the hardware, not the operating system).
Set up: It couldn't have been easier. Remove from box. Plug in the power. Plug in the keyboard. Plug the mouse into the keyboard. Press the power button.
Keyboard: not my favorite. Oh it's gorgeous to look at, but it lacks a 10 key pad. The general feel and operation of the keys are both smooth and comfortable, but I prefer to have a 10 key pad.
Mouse: It has a great feel. It's primary button is the entire body, while it also has buttons on the side. These activate a window minimizing function which facilitates switching windows. The mouse also has a track ball on the top with allows scrolling.
Ports: There are 4; however, you need to use 1 just for the keyboard. So, you effectively only have 3 USB ports. There is 1 firewire, and an ethernet port as well. Unfortunately there isn't an analog telephone jack. If you're stuck with dial up, you'll have to purchase a USB modem. Likewise if you want to send faxes, you'll need that modem.
Included software: While you don't need to purchase iMac 24" to get the include software, it does come with iLife (itunes, iphoto, imovie, idvd, garage band, et al). The included software is very useful and helps make using this computer that much easier. You'll still need to get some productivity software (ie: Office, iWork, what-have-you).
Processing Speed: I don't have technical statistics, I can only give you my subjective impression of its speed. I think it's fast. Much faster than my eMachine it replaces; however, I should mention that it was a '03 Athlon model, so you can't really compare the two. It is faster than our '08 MacBook, but that is just a function of more power. The processors are the same.
All-In-One: While it was nice to get a huge, beautiful screen, with the computer, an AIO design means the failure of one part is a failure of the whole unit. I'm a little unnerved by that, but I didn't have to buy a separate monitor either.
Expandability: Not really. Pretty much what you bought is what you get. There is a slot to upgrade/increase the RAM, but economically, you probably should have bought a next bigger machine or gone Mac Pro if you wanted upgradability.
Why iMac?Ultimately it came down to ease of use and a total dislike of Vista. While similarly equipped Intel Core Duo's in Vista machines will cost you less, an OS X machine seems to be less "buggy." We figured the time avoiding de-bugging the operating system was worth the additional cost.