Good choice Chris!
I've just spent the last 2 weeks hacking up phpBB2 for my (soon to be re-launched) Gresley Rovers site.
There are a few things I fixed, and if I spot anything else in mine which is manky I'll let you know.
One thing I would do though is give the Emoticons on the post page a width and height, otherwise the page is stretched until they're loaded (in IE). I'd also do the same for the New Topic, Hot Topic etc icons on the view forum page.
Matt
Oh, and one more thing. I'll quote a couple of posts from the past:
Matt: "Why don't you [Chris] use a database to store all the posts rather than loads of html files."
Chris: "Using a database for a forum is a bad idea, a *very* bad idea."
HAHAAAAAAAAAA!