Ubuntu:
Positive:
-Effective 64-bit OS so far.
-No viruses, built in security
-It's free
Drawbacks:
-Can't find a good ogm/mkv player
-Driver issues(sound, video)
-Learning curve on the GUI/CLI switches
Vista:
Positive:
-effectively utilizes the speed of new technology
-Direct X 10, and gaming
-eye candy
Drawback:
-runs like molasses on older machines
-annoying security features, UAC for example
-eye candy eats resources
XP:
Positives:
-tried, tested, comfortable
-most software works on it
-less annoying than Vista
Negatives:
-Does not like new technology(it took me 12 hours to fix a HD Audio issue)
-It's showing it's age(lack of multiprocessor support, RAM over 4GB, 32-bit limits)
-Doesn't come with drive encryption like Vista and Ubuntu.
As soon as ubuntu offers better driver support, a good mkv/ogm player, and I can use gametap on it, I'm going straight ubuntu.