I don't know if this was posted before. At least, I could not find it using the "search".
Say you search for MtGox, looking for latest about MtGox, you will get pretty much everything *except* what you are looking for. Sometimes I think it has some sadistic intelligence and guesses what you need to give you something entirely different.
And what is this "relevance"? Doesn't make any sense.
I agree, it's not the best search tool, but it usually helps if you know what subforum the topic you're searching for is in. I can't count how many times I've searched for something important and then realized it was searching through all "off-topic" topics or something similar.