I think this might be the problem of a StackExchange for a particular Linux distribution. Where do you draw the line? I believe that there are currently nine variants of Ubuntu fully supported by Canonical - Ubuntu, Ubuntu Netbook Edition, Kubunty, Xubuntu, Edubuntu, Gobuntu, Lubuntu, and Ubuntu JeOS, and Ubuntu Light. These are the versions that, in my opinion, should be on-topic for this site.
The problem with the variants not officially supported by Canonical is that there's no control over them - they could deviate widely from Ubuntu. Someone who is experienced with Ubuntu could probably address questions related to most, if not all, of these distributions.
But this kind of debate brings up my biggest concern with separate StackExchanges for different Linux distributions. I use Ubuntu, but I've very easily sat down at other Linux distros - OpenSUSE, Arch, Debian, Fedora - and been able to use my Ubuntu experiences to help me. There are some differences between the distros, but honestly, differentiating between Debian and Ubuntu and Ubuntu derivatives isn't easy and not that productive when you start to get the same questions across all of the sites. But that's a whole other story.