There were definitely some bugs around the filtering / content loading. I _think_ they've been resolved for a while now, so I hope you'll give it another shot.
No problem. I definitely will, because I'm enough of a completist in general that it bothers me when feel I've missed something that looks interesting, and I'm already seeing that again. Well done, you've created something that immediately triggers (because I can see what I was missing) and alleviates (because I can check what I missed) my obsessive behavior over HN. Next step, profit as I throw money at you... ;)
Oh, and if you're looking for recommendations on new features:
1. Colorize submissions that have had X% increase in votes/comments (with different colors) since last visit when in top X mode (specifically in the past 48-72 hours).
2. Allow a user defined point/comment threshold over which submissions are colorized.