Since I use JomSocial I needed a plugin to integrate Compojoom Comment with the Activity Stream, I found one on the Compojoom site. The plugin was old and didn't work with 1.7. I wrote a question about it in the support forum, and suddenly there was an updated plugin available! Wow! That's something you won't get everywhere, support this fast and this good is hard to come by!
Compojoom Comment is a very good commenting platform and has all the features you would expect, the import function seems to be able to import from almost any commenting systems.