Ubuntu (Gnome) 9.10 worked fine on my T43 "out of the box" too, and apart from Grub2 trying to sneak itself into my setup ("hidden" advanced option on install) it was surprisingly painless, given the large amount of negative feedback I've seen elsewhere - which IMHO is mostly down to folk not taking the time to understand what they are doing! Blue skies, sunshine and beach intervened in my weekend plan to try kubuntu
As I mentioned earlier, my personal dislike of Ubuntu is down to it trying to be too user-friendly; which is probably exactly why it is "popular" (i.e. used by a lot of people).
BTW, the fact that it (Ubuntu) is "based on" Debian will bear little relation to how it will work (or not) on specific hardware. As an example of the subtle differences, there have been two revisions of the "radeon" driver during openSuse11.2 "release candidate" phase alone, to try & solve problems with some of those ATI cards, so even within the lifetime of a specific release there will can a multitude of different potential combinations of kernel, modules, drivers and application packages, never mind comparing between distros. And different distros have different policies on how much evolution they will enable/allow within the release lifetime
Again, there is no easy answer to the thread's original question.
IG