Gnome 3 seems to be finished. It looks great. When can I use it on an installed Linux distribution? In May, on Fedora, and in October, in Ubuntu. On Debian Stable, I'll have to wait a couple of years. I'd be tempted to install Fedora, but my CD drive is failing.
Update: Status of Gnome 3 in Debian.
Dark green means Gnome 3 packages are up to date in Debian Testing. As you can see, there isn't much dark green.
Update: apt-get install debian-wizard has a good post on installing Gnome 3 in Debian: in summary, as a comment points out, Gnome 3 may be "made of easy", but installing it on Debian Squeeze isn't: it's for Linux experts only, requiring Debian Testing plus Experimental repositories. The blog does hint at what may be the best compromise for Debian Squeeze users eager to try Gnome 3: install Testing and wait for Gnome 3 to "land" there. The status site linked to above shows that Testing is making progress towards Gnome 2- but no ETA yet!