I dunno, I think the search function works pretty well. Tons better than before! The only thing that drives me nuts is the PM system. A bit clunky (sometimes I have to login again, although I'm already logged in, for example). But more so, not seeing the message that I'm typing a response to and not having a copy of what I sent. Some of it is good info that could see further use, or be posted, or whatever.
Otherwise I wouldn't change much. I wouldn't want a chat function (which would negate the "online now" thing). We could all stand to take a breath and get over the need for instantaneous gratification. I also like the more public form of communication here; keeps more people in the loop, gets info out there that otherwise wouldn't, probably keeps things more civil.
EDIT: One thing that would be nice is a "watch" function, so you can tag and follow certain threads. And/or a "library" function, to permanently add a thread link to your profile's, um, library.