I already had objections moving away from my loved Windows 2000 to XP, but finally, XP turned out to work stable enough. It caused CTDs for sometime because I had damaged memory modules and XP was more touchy for these problems (2000 ran perfectly on the same memory, I have never found out why).
My ideal successor windows would be somewhere between XP and Windows 2000 actually. There is a lot of stuff I don't need in XP and the functions of Windows 2000 had been great for me. And finally, most of the professional stuff I learned for operating Windows NT 4.0, worked well for Windows 2000 and after a short reorientation, also for Windows XP.
Vista on the other hand, is a pain in the ass, from what I notice when looking how friends do with it.
Linux on the other hand is for me a nice toy. I like running an installation once per month and sometimes test software for linux, but since the invention of Linux live distributions like Knoppix or Knoppizilin, I don't even need to have a full linux install here for such stuff.
For workstation stuff, I am also close to testing OpenSolaris.
When I move together with my girlfriend, I will assemble a small passive cooled ITX cube for running the network stuff on Linux, as I have to leave all my network infrastructure here.
