I actually am in an IT class and for what ever reason they are apart of some alliance with them and all the students (me included) can download all MS OS's and a lot of other MS software for free, and get legal keys to go with that, so I'm excited about that. But this saves a lot of money too. I'm running the RC of W7 right now and I like it... better then vista for sure.
Millions of torrent sites are also giving it away, for free, and to anyone willing to work without it enclosed in an annoying case. Guess what, they even deliver it to you, and place it on your desktop.
Additionally, the only OS I am looking towards is Backtrack4, I've been stuck with 3 for too long, I don't have any disks larger then 700mb soh.
Windows XP is still better in my opinion. Obviously not for security, the windows 7 security improvements have surprised me. But hey, if you're after security, and you really think someone is going to attack you, you're probably running a server, in thus case, it should be on linux.