I've just installed Ubuntu -
http://www.ubuntulinux.org/ - on a dopey old PII
Detected everything and installed without a murmur - the updated Gnome desktop (and I'm an old KDE fan) is really impressive. At last they've got the onscreen fonts nice. And even on a 233 processor and 128Mb it runs acceptably and usably - amazing! SuSE 9.2 was too slow to be much use on this antique (which normally works just as a print server).
We're revamping the computers in the practice and while we have to retain Windows on three PCs (the billing software is Windows only) the 4 PCs used by other staff will go over to Ubuntu Linux from 98SE.
Anmd what's more, we're standardising on OpenOffice 2 all round. Finally, the suite hits the sweet spot.
I dunno how much we're going to save, but I suspect that it'll be a lot. Less antivirus software for a start. If we were going with Vista/Longhorn we'd have had to buy 7 new PCs.
Oh yes, and there is the satisfaction of giving a bit less support to a convicted (and unrepentant) monopolist.