Well, I've only had the Habari source installed for less than a week and I've already contributed and helped to resolve a bug (#182). The Habari guys, in this case moeffju, are pretty damn quick at sorting things like this out if you're able to actively work with them via IRC and using SVN. I think I'm going to enjoy using Habari.
Now the SVN works without the need for me to make any changes, I think I'll start working towards migrating my sites across. First I need to add some sub-page functionality though.