The following is a quick HOWTO for the brave Debian users who want to upgrade to GNOME 3. Assuming you have an up to date system running sid, and experimental listed in your APT sources, perform the following complicated steps to end up having a functional GNOME 3 desktop:
apt-get install -t experimental gnome
Thanks go to Joss for putting together new GNOME 3 meta-packages, and the rest of the Debian GNOME people for months of hard planning and packaging work, and painful testing transition handling.
Before you ask, yeah, not all of GNOME 3.x is in unstable yet, but will soon be, as precedent transitions start clearing the way. And yeah, GNOME 3.2 will come just after the two remaining package sets enter testing. To compensate, you'll find that you have some GNOME leaf packages pending an upgrade to 3.2.0-1 while you read this.