I did it once.
Played our arses off and were by far the best band in our "heat" (TOOT TOOT! there goes me parping my own trumpet... I am being serious though), had the most friends there, went down the best etc.
Three judges on the "panel" of which two we knew and voted for us (as we asked them and they aint liars), and we still lost as the other ahem... "judge" had something to do with the event and thought the other band were "nicer" and apparantly wanted to manage them.
Make of that what you will...