> The notification sytem will start out pretty basic. But it will at least let me migrate from showing total PM count to just showing unread PM count. I'm also keeping it generalized so that I can eventually support notifications for things like:
> 
> - Mentions. Maybe something like `[@]El Taco Taco[/@]` and when you're quoted in a topic.
> - New posts in subscribed topics.

How do you plan to do unread notifications in threads? For example, my favorite forum software (SMF) has a topic log in its database with the member id, topic/thread id and the id of the last message id viewed (which I believe is an AJAX call for browsers with JS enabled, and a message included with POST when users access a new topic page for disabled JS browsers like WAP or Lynx). That makes it simple (relatively so) to handle indicators of new posts by comparing the topic's latest message id with the topic log.