I have a couple suggestions that would make things easier for me:
It'd be nice if there was a way to sort topics in the reverse of how they're sorted currently (especially for the "active topics" screen). I normally have the site open on one tab and just check back and refresh periodically and scan through the topics that changed since the last one that was on the screen before the refresh. That all works great, but right after the topics roll over to another page there's like 3 topics there and I have to pull up another tab with the stuff that's a little older. If the topics where sorted so that the most recently active topic was the first one on page 1, I'd never have that problem. It's a minor issue, but I'm anal about efficiency, so it hurts my soul when I have to do extra clicks
A "quote" button on other people's posts that would stick the block quotes of their post into the reply text box, maybe with their username as well. This is common on other forums I've used and it really makes it easier to consistently show who you're responding to (if you're responding specifically to someone else's post). Very handy, IMO.
If you took the quote thing a step further, you could make it so that there's no way the user can edit the text he's quoting in his post. That'd fix the editing issues being discussed as well, because everyone would be able to see what someone's post said at the time of the reply.