I'm liking Habari more and more as I use it. Not that there aren't issues. Of course there are! It's still alpha software.
An important issue I've run into is the reliance on database specific queries. These make it into core code, which can't be helped. However, if the software is supposed to run on more than one type of database, these database specific queries have to be translated into forms other database systems can understand, or gracefully ignored.
Habari solves this issue by having all queries sent to a translator function, a good idea, but it only works if a translation is actually created.