Currently only unstable (sid) is supported. Squeeze (current testing) will be supported once python-gobject >= 2.16 enters testing.
In order to install sugar-jhbuild, you need git-core and svn.
After installing and updating sugar-jhbuild according to the common instructions, you can use this invocation to install all dependencies automatically:
./sugar-jhbuild depscheck -s | sudo xargs aptitude -y install
To work around a bug in the Gnome Python bindings, you need to issue the following commands after installing all dependencies:
sudo aptitude install chrpath find /usr/lib/python-support/python-gnome2/python2.5/gtk-2.0 -name "*.so" | sudo xargs chrpath -d