I've been using the desktop version for about a month now. I have no complaints really, but I didn't really see any major differences between 10.04 personally. The default theme got a bit more orange, but that's about all I noticed
I've been having an issue with GDM lately... I seem to recall it happening in 10.04 for a brief period of time as well, but I'm not sure. At boot, gdm stops responding when I open a window, any application. I enter tty1, stop then start gdm, and all is well until the next reboot. Haven't had the time, or cared enough really to seek out a possible fix.
Kubuntu 10.10 was great in a VM but as a Live environment I had graphical corruption, especially with GTK+ applications, and pasting from the clipboard took around 1/3 of a second. Holding down ctrl+v and then releasing it caused it to just sit there slowly pasting the clipboard contents over and over until it had done it as many times as I had "pressed" the key.
10.10 is the best of the three Ubuntu distros I have tried so far. starting with 9.10. Not a great difference from 10.04 except the kernel , driver , software , and my title bar no longer disappears at random .