Took the plunge and installed 10.04 from scratch on my PanP4 and so far, so good. Very impressed and no problems to speak of. A lot quicker, but I have not bothered with Compiz this time (can go without the bell-whistles that I hardly used anyway).
Only complaint is the new Ubuntu splash screen, which looks really bad (640x480). It was ok just running the Live CD, but changed to a lower resolution when I installed the NVIDIA driver (173).
Anyone else had this problem and got a fix or will it be a wait for a new driver?