Fedora 10 alpha is very, very early in the cycle. You won't get access to anything else as early unless you're actually working on it yourself and that is the point: if you want to get involved very early on you can do.
Fedora 9 gave a much-needed impetus to the KDE 4.0 work and while KDE 4.0.5 undoubtedly has a lot of rough edges, it's much better for the extensive testing and fixing that it got through the Fedora exposure -- KDE 4.1 (and Fedora 10) hold great promise as a result.
Fedora, any release, though can be seen as the enthusiasts distro: it has everything bar the kitchen sink (I checked) and the latest version of all of those things. By its very nature it's not stable although I have less trouble with it than I do with Windows (except that I hardly use Windows any more).
If you want crave stability and you want to stick with Red Hat, then go for RHEL or CentOS. Of course, you won't get the latest of everything and your favourite package probably won't be updated ("rebased") for the lifetime of the release, but it's stable and well-tested and the only time they get rebooted is when the kernel gets a security fix or when the next update for the series comes along. Or some idiot trips over the power lead.
You could write practically the same about Ubuntu and Ubuntu LTS -- the enthusiast releases will never have the stability that the long-term support releases have.