czl, that is probably the best way to go, clean install on a separate hard drive. In my case, I did a clean install, but on a hard drive with a few other distros present. It worked out, but I did think that things were a bit tricky with this new installer.
As for GNOME 3 and GNOME Shell, to each their own. I first started using it in Fedora 16 and liked it then. Went with KDE in F17, then back to GNOME Shell in F18. My opinion is that it's "ready" if you're ready for it.
But that's just my opinion; obviously, many people would disagree!