Leopard is cool and all, but that's a lot of money to plunk down.
Personally, my XP Pro system works really nicely and looks great with Stardock's WindowBlinds and ObjectDock. I customize my sounds, and I love it.
Ubuntu Gutsy Gibbon is a great alternative because it's free, and very nice to use.
I would only get a Mac if I wanted to do serious video editing, and Vista.... bah! Only if I wanted to play DX10 games, which there isn't anything worth it that's out right now. As far as the Vista look, WindowBlinds is much nicer. Although I will admit that the animated wallpaper in Vista Ultimate has me interested. I think it's called DreamWeaver or something. :-)
