In the forums, if you put any quotes in your search string, the result is a 500 error.
But I've noticed if you search for something with quotes, get the 500 error, hit Back, and do the same search again, you get a normal search result page. Though none of the results seem to contain what you searched for.
A wiki/content search (top of the page) in quotes will work, though the sort order is different than if you searched without quotes. Ex. Searching for SimCity gets you results in a different order than "SimCity". But then Dave mentioned sort order in the "What we're working on" thread, so maybe this will change.