I don't know what you're trying to say regarding distros, but surely distros do configure and even patch the kernels differently, so you can't compare a certain vanilla kernel version with for instance "Fedora 8". But even if you could, do you think it's reasonable to refer to Fedora releases instead of kernel versions? Am I supposed to know whatever kernel Fedora X uses? To me, that's completely irrelevant. I will never care even remotely whatever kernel version Distro X, version Y uses. I simply don't care, and I shouldn't have too, since I'm not using that Distro damn it!
We all speak out of experience with the so far drivers. Many of us see a pattern of not caring about really fixing the sucky drivers, but just fixing a bug a month, and this time, making the driver get a better score on FPS benchmarks.
Anyway. I've got some answers now.
* No RandR 1.2, because ATI has invented their own proprietary tool before RandR 1.2 was invented, and because of that (very interesting reason) they won't use RandR 1.2 even though it's superior.
* 2.6.22 _should_ work. Well, 2.6.20 _should_ have worked (if you ask me) a long time ago. Will they have fixed support for 3 major kernel versions in a row? OMFG. Unbelievable. And highly unlikely :/
Well well, we'll see... Maybe the "open source" driver ATI will release in a couple of decades, and which will have become well tested and patched a few decades after that, will be interesting.
But ATI surely doesn't understand open source development. Release a 50 mb .tar.bz2 and say "we're now open source" is lunacy. Release _early_ and _often_. This way, important and highly skilled people (I'm thinking of X.org developers) can pin-point flaws and comment how things should be interfaced, to work better with X.org.
Otherwise, it might be "open" but it'll take a _long_ time until it'll "work like a charm" with "just about any linux kernel, distro, X.org-version", which the currently support drivers more or less do.
But ATI probably just want being tagged as "open source friendly" instead of really being interested in community development.
Again, I'm speaking ahead of time, but it doesn't take many brain cells to figure out what's going on here. I'm not saying I'm guaranteeing the new ATI driver to suck, I'm just saying it most likely will.