Just slightly OT but does anyone use Ubuntu I'm thinking of getting it
What's your level of dependency on windows apps? before I switched I was already using Thunderbird for email, Firefox as browser, OpenOffice as an office suite, Filezilla for FTP, Pidgin for icq/gtalk/msn, Picasa for photo organization.
I adapted and started using Amarok for mp3 player, and a few other apps that I preferred after testing the default and a few of the other optionally available apps.
I've even got some windows apps running inside ubuntu by using Wine, including a few games. It's not always that easy, but if your patient and google, and read help forums, there's usually guides for most things.
Failing that, you can always install Sun Virtualbox and run a windows (95/98/2k/XP/Vista/7/whatever you prefer) Virtual machine for any absolutely cannot lose apps.
Also, I believe there's an option on the Ubuntu live cd to install inside an existing windows partition, from within windows, and thus you lose nothing, and you can switch back and forth with a reboot. You can also boot off the CD and try it out without installing anything.