I'm using the downloaded version of Mandriva Linux right now and it's amazing. It has Firefox, a couple of nice HTML editors, OpenOffice, a good FTP client, a useful FTP server, and a client for terminal services that is somehow more reliable than the one packaged with WinXP. The screen savers are the sort of thing a scientist would like. Linux also reminds me of the computers that I used at college, so I feel at home with it. I'm also amazed at how popular I have become after becoming a Linux user - Every day, I feel like some kind of really wild rock star.
