I just completed a version upgrade from Intrepid to Jaunty. Intrepid was running Gnome and the disk used was a daily build of Jaunty Kubuntu. The entire process was very slick with only 3 decisions to be made by me during the process. This is the first version upgrade I've done since I tried to upgrade 7.10 to 8.10 with disastrous results: it left my system in an unusable state. So far, I have not found any issues though I suspect some may pop up as I work more with the system. In the end I was left with the exact programs that I started with and no new ones with the exception of a few things being different in the system menu and I still have Gnome as the default desktop. I'm very satisfied with the process.