As of last night I'm officially an Ubuntu user. Things have gone pretty well so far, although Evolution seems to have some kind of leak because towards the end of the day I noticed my system slowing down, and a quick check in the System Monitor showed Evolution using 780MB of RAM and 25% CPU! I watched the RAM usage slowly grow for a few megs, during which time Evolution did not appear to be doing anything. I re-started it and the memory usage dropped back to the normal 20MB or so and my system became snappy again. Definitely another impetus to find an alternative.
Now lets talk about some things I like. Performance is the first thing. Everything just seems faster. Perhaps it isn't fair because I don't have nearly the list of services running and I need to use XP VM's to do a lot of tasks, but for anything I do within Ubuntu itself I really feel like the speed is much faster. Apps load faster, things respond to my actions quicker, and the file system manager (Nautilus I think) seems quicker than Explorer.
The other big plus so far is the window management. I absolutely love the virtual workspaces, and using the keyboard shortcuts to switch between them is starting to feel natural. Moving between them is quick and seamless, and it just gives the feel that I 'have all of my stuff spread out on my desk'. That's the best analogy I can think of.
Finally, tonight I've been playing with the neat desktop effects. I tried the famous Cube but I couldn't get all the effects to work (not sure why) and I find the default Wall behaviour to be more natural and efficient anyways. The zoom feature is great, I should get some use out of that, and the Expose feature might be useful as well (if all those Mac zealots can be believed). Last but not least are the eye candy effects, like wobbly-windows and whatnot, which I assumed would hurt performance but don't seem to really have any effect at all (aside from being neat).
All in all the jury is still out on how functional this can be given my Microsoft-centric career, but I would not hesitate to use Ubuntu on a home PC. Not my Mom's home PC, mind you, because despite all the fervor around how user-friendly Ubuntu is, there is a LOOOONG way to go. I may be crazy, but I'm not THAT crazy.