It has been some time since the last debugger release, but now it's finally ready - version 0.30 "Koblenz" of the Mono Debugger has just been released :-)
The big news is that there are now binary packages available for a number of distros - they can be found at http://www.mono-project.com/Downloads. The source tarball can be found here.
There are a lot of stability improvements in this release and the debugger has also been tested on i386.
Btw. the release name is some kind of an "in-joke" - I'm reserving the name "Cologne" for a stable, 1.0-like, release - and Koblenz is about half the distance to Cologne from where I live.
Update: I have been asked about the binary packages since they are a bit hard to find. On http://www.mono-project.com/Downloads, select your distro - for instance "SuSE Linux Enterprise 9 x86_64" - and then follow the "latest" link. This'll lead you to http://www.go-mono.com/download-latest/sles-9-x86_64 where you find the debugger package in the "Development Tools" section.