The main reason I use the search function is to find a topic that I was reading recently, but has dropped off the recent posts/ trending topics list - using a couple of keywords I remember from the forum posts.  The serach results don't really help in this scenario, lots of (admittedly relevent) results from 2008 but never the actual thread I'm looking for. Have you thought about weighting the results more by recent date, or including different options for search, by date / by relevence / other ?