New user notifications were actually added in the 3.1 release, due to user requests. However, upon looking at the code, we realize it's only sending them if the "Create New Users" setting is configured for "Full Joomla User". If you have it configured this way, and aren't getting them, let us know. I've added a task to add similar functionality to the "Facebook User Only" option in the next release.
As for comments, we agree. We're working on big improvements for the comment system right now that will start being introduced in the 3.2 release. We're somewhat limited by what Facebook will let us do, in some areas, but our goal is to make administering comments (and a lot of the different interactions between your site and Facebook) much simpler in the next few releases.
Thanks for your feedback, and let us know if there's anything else we can help with!
I want notifications. Possible?
