I had this question in my head through the whole essay and the top commenter beat me to it.
I've heard thousands of issues with the new Ubuntu release (never bothered trying it myself). I doubt I'll recommend Ubuntu to anyone I know who's interested in Linux for quite a while. I've had great experiences with several of non-Ubuntu distros and will probably recommend them instead.
-- jwz, 2002
But I guess this is the problem, right? New problems always arise in different distros and different versions. I can't say I've found one distro to commonly recommend because it seems like all of them have had problems at some point, even in newer releases.
For me, I don't care as much about switching distros. I have my .emacs setup and my files, it's easy to move. But for a lot of people, I think they want something that is almost always stable so they don't have to switch distros or put up with bugs.
Can't say for sure, but it also seems like Firefox behaves differently between distros, as if the code in the repositories differs drastically enough to offer a dramatic performance boost. Granted these are not scientific observations and I'd defer to someone who ran *buntu vs another distro on two boxes with identical specs.