What I don't like:
Can't always tab between buttons, even with "full control" (or whatever it's called) turned on in the "Keyboard and Mouse" prefs.
When connecting my laptop to a network drive: putting the computer in "sleep" mode without disconnecting the mapped drive and then bringing the laptop home, open it up, computer can't find the network drive anymore, and it hangs up my computer for like 30 seconds (beach ball of death). Windows handles this MUCH better.
"Sleep" mode has never worked properly on any Apple *desktop* I've ever owned, except for my new iMac. Never has worked correctly on my DP G5, never worked correctly on my DP G4.
My G5 at work will randomly send the fans into "full blast mode" and the machine locks up completely. This is when I'm not there, not even using it.