I have a problem with the interface. It looks a bit scary and cluttered the first time you see it. Lots of buttons, lots of tooltips, etc. With this in mind, look at this concept, progressive reduction. My idea is not exactly the one in the article, but instead to show a minimal interface at first, and once the user gets familiar with it, present more advanced functionality gradually. The idea of progressive reduction could also work here. So, each user would see the interface differently according to how much they’re used to the site’s interface.
An examples where this would be cool to implement is the “format” toolbar when writing a post. Maybe at first you can only write plain test. My idea is not exactly to limit functionality (like the idea of unlocking features in Stack Overflow), but to kinda hide it so that new users are not scared when they first visit the site.