I run testing on my laptop (Gnome 2.2/2.4), but just for kicks I always have a parallell install with the latest Garnome
Gnome release - currently Garnome 0.28.2, which provides the Gnome 2.5 development branch. It's very handy since it doesn't break anything - it is in fact a separate installation of Gnome and its support libraries. I always install it to /usr/local/garnome (instead of to ~/garnome) so all users on the computer can benefit from it if they wish.
It is very easy to install, but it takes a *lot* of time as it builds everything from source.