Your experience with Mac OS X seems profoundly mixed so far. I'm a little surprised that you disliked top-posting so much - I think that's at least partly because I've never used bottom-posting.
I agree with you about iTunes - it makes managing your iPod and your music collection simple. If you're like me, and have to tag songs yourself often, you should check out Doug's AppleScripts for iTunes - there are some useful scripts there for automating various iTunes tasks.
Compile 'em all said:Bottom-posting is the defacto standard on most usenet groups and technical mailing lists. YMMV of course.