I'll repeat the comment above about design :What I like is the brilliant interface of the forum/discussion board, where threads are brought to the top of a discrete list according to the most recent post, even if the thread was otherwise dead as of long ago

Other forums I am on do something similar - but I think the 'cat does it best.

The search facilities are the best I have run across on any bulletin board/forum. For all the foibles and quirks (and we all know the searches have them) I get better more consistant results with the searches on the cat then I do on any other site I've frequented.