I've successfully installed latest Monodevelop on Gutsy. It works very well, including Boo syntax highlighting and inline MonoDoc references ( pressing F1 key)
The light comes up to me when I've found this post
So, from there I've downloaded the mono-addins and mono-0.19 .deb packages.
After that I've downloaded monodevelop-boo.rpm from openSuse and converted it to a deb package.
For monodoc i've downloaded the monodoc_1.2.6-2~bpo40+1_all.deb backport package.
Latest boo deb package was downloaded directly from the official site, it works well.
I've installed my 5, fresh, Mono and Boo packages and... voilà, I've got a perfect MonoDevelop installation, with a working Boo addin with syntax highlighting and a MonoDoc browser correctly linked with the IDE.