OZ also tends to be the most up to date - for example I'm running 2.6.14-rcX on my c7x0 and efforts are underway to port 2.6.x to the 5500 (though there are issues regarding the use of SD cards due to an undocumented Sharp chip in there). I'm also using libc 2.3.x, etc.
So basically, OZ is the most up to date distro around. Now someone is bound to pipe up and say this makes it unstable, and it has to be said that some releases have had issues, but I've personally not had any problems I couldn't fix,
If nothing else, my post will start other people posting...
Si