The searches work very well. The only thing that may be confusing for some users is the Forum filter. It defaults to the forum you're currently in, which is fine, but they may not know to click that button and select more filters if they can't find what they're looking for. Two of my searches returned no results which got me to select more forums. Can you add a user tip to that button. or change the sentence that appears with 'no results' or give the button a different color?
A good thing about the forum filter button is that it defaults to all forums if you're searching from the main forum page.