Ubuntu never installed succesfully over here, part of the reason why I never gave it any attention really.
However , I was Beta testing Fedora Core 5 on a spare PII machine, after seeing what I wanted to see I decided to give Ubuntu another attempt, but this time instead of Hoary Hedgehog I tried the 5.10 Breezy and Easy 😛
Surprise Ubuntu now works for the first time !!! I think they have finally fixed the bug that was stopping me from running it on all of my machines. I was having kind of the same problem as you were, instead of being directed to a GUI,but I got no errors and just found myself at the commandline ! GDM couldn't launch succesfully.
Ubuntu was not bad really for me as a Fedora user, I LOVED how fast and stable Synaptic is as compared to YUM, but that was about it, really 🙁 couldn't find anything else in Ubuntu to keep it on that machine, however I am keeping it there untill Fedora Core 5 goes official.
However I need to ask, what version of Ubuntu do you have ? In case you are running an older version, try and get the 5.10 certain bugs might be fixed by now,