First time Mac user since Nov 24 on an iMac 21.5" 500 GB

. Used Windows since 1991. Happy overall with my iMac. Some things take getting used to.
Annoyances:
1) Finder has no cut feature. Must drag/drop files to move them. Also, files and folders aren't grouped separately in an alphabetical list. A 3rd party $40 program called Pathfinder will fix these issues.
2) Must resize all windows at the bottom right hand corner.
3) Some webpages take longer to load on Mac vs Windows (using Safari, Firefox, Google Chrome).
4) No 1-click "hide all" or "show desktop" although can achieve same result through Spaces.
5) Programs assigned to a Space don't always stay there.
6) Reflective screen takes getting used to.
7) Time machine only lets you select what you *don't* want to back up. I wish it would let me chose only what I *do* want.
8) Syncing up my iPod occassionally crashes the computer (others on web have reported same issue).
9) Camera quality isn't as good as say the iPod Nano 5G (but not a big deal)
10) Mouse/keyboard take getting used to ergonomically. No number pad on the keyboard. Right clicking takes some practice. Wireless never seems to track quite as well as a cable mouse.
11) $1200 *starting* for an iMac.
12) Entry level graphics cards below industry standards for overall price (not a big deal for me since I don't have time to play, but its the thought that counts right?).
13) Crashed 3 x 1st month. But take into account that I'm installing a lot of 3rd party stuff.
14) Menu bar is at the top of the screen instead of the application window. Must remember to select the app you want before using the bar (not a big deal, but it takes getting used to).
15) Allow/Deny glitch with new programs. The window flashes for <1 sec before going away, but comes back when you try to do new things on the 3rd party program. You have to be quick to hit the Allow button to stop it from coming back.
16) Must add 3rd party drivers to write to NTFS files.
17) Galling to admit, but I could get done everything that I wanted on a Windows PC for half the price. Windows 7 is *almost* as a stable an OS as Snow Leopard from what I hear. Given that you can buy an i7 for around $1000, speed isn't likely to be an issue with Windows anymore.
Likes
1) Unmatched *cool*

factor - the iMac looks like it came off a Star Trek episode.
2) Fast processing. The Core Duo handles things just fine now, so the i7 should keep things running quickly that much longer for the life of the computer.
3) LED backlight is DAZZLING!
4) Built-in speakers, camera, microphone.
5) No stinkin tower!
6) Wireless keyboard/mouse.
7) Magic Mouse's touch only surface is AWESOME.
Love the inertial scrolling.
8) Can install Windows on it if you need to. It is $160-$200 for a copy of Win 7 or $90-$100 for Win XP. Just please don't buy ever use Vista. That's just sick.
9) Can upgrade RAM easily on an iMac.
10) Plenty of productivity options: MS Office for Mac for $130, iWork 09 for $80 (cheaper on ebay), or Open Office for free.
11) Expose is a dead useful feature! You can see what you are looking for and just click it to bring it up.
12) Spaces can give each application its own desktop if you like. Or group some apps in the same desktop.
13) Dashboard is handy for loading apps that will show you in one click the weather, radar, CPU usage, daily comics, and a clock you can see from across the room.
14) The Dock works much like a task bar. Very easy to learn for me.
15) iPhoto slideshow is a professional presentation. You'll love it.
16) My 2 year old son loves playing with it (yes, I had to throw that in there)
I'm sure I could go on, but 30+ bullets is probably enough to get you started. Hope this was helpful.