OSX is a pretty user friendly OS so you shouldn't have any problems, it will just take some getting used to to, like any new thing does. I like the fact that boots very fast compared to Windows and shuts down very fast compared to windows.
Ok, for one. keep your windows xp cd. download BootCamp from apple(if your getting a new one, it should already come with it)
with that you can use windows nativly AND mac. beautiful huh
next is, if your a gamer, dont switch...mac = bad gaming, UNLESS you get the mac pro and then boot camp.
mac is pretty basic. runs under the safe and stable "unix."
if ur a real hardcore computer user who likes to spend his time learning a poopload of code, go to linux.
I dont think its worth it, simply becuase i dont have time. but linux is very good and fast.