First of all, congrats with getting this from the ground. I see the potential, especially with RSS feeds. Valid XHTML and CSS? Wonderful! Go teach slashdot ;) But -there's always a "but" coming after praise- the navigation of the posts/threads seems really hard and non-intuitive. I've looked around for a bit now and just find it hard to:
* Read a thread
* Read a single post!
Maybe it's just me, but I guess you may scare people off with this interface. A tree view of the thread might help (indent here and there)? Also the different colors in a single post are not really helpful to get a quick overview IMHO...