Forced users: the profile system with xp, and the extra navigating that one has to do ie,
C:/Documents and Settings/Users/User_Name is annoying.

*nix is infinitely more difficult to mess with than XP. Firstly, you require root access to change anything major on the computer. So unless you have the password, you can't do shiite without the user of the comp doing it for you. Meaning that, if you want to break a *nix computer the user has to assist you in doing so, wether they know it or not.

The restarts are annoying, wether you wait until later to do them or not, I like leaving my computer at the ready all the time. Unfortunately, with XP, if you want major software changes to take place - you HAVE to restart.

Some articles of interest with respect to the security issue ( There was one that I really wanted to copy here but I can't find it! )
AGAINST *nix
http://www.linuxsucks.org/read.html?postid=5595&replies=47

FOR *nix
http://search.linuxsecurity.com/feature_stories/interview-avi-2.html

Although, of course, one must remember where information is coming from. Both sites would show bias in opposing directions.

Peace!