No, I'm still using Vista on the main PC (this one). The Ubuntu (strictly speaking Kubuntu because of KDE) is intended only as a server for messing with web dev stuff. To be honest, I built it because I could - the PC was there, Ubuntu was free (or nearly so - bought a disk rather than download), there was a spare port on my Netgear router, and I wanted to give it a go.
I only really installed KDE, because the server install by itself is a command line only operation, which would mean I'd have to learn a whole bunch of Linux stuff right off the bat, before I could do anything. KDE at least gives me a GUI and gives the mouse a purpose in life again. It kind of eases me into playing around with this stuff and expanding my knowledge a bit.
As far as I know, KDE doesn't come with anything specific for photo-editing, or at least not that I've spotted yet. I do see a fair few mentions of GIMP around the forums though and have seen some good results from it on flickr. Not sure whether that can do RAW though. My photo editing is going to stay Windows based I think, especially as I'm expecting a student edition of CS4 Web Premium for Christmas.