Yeah, I'm a SpongeBob fan, (a fact I think I mentioned here a while back). So of course I had to go see this. I actually saw it in the theatre, but just rented it for the kids again.
I seem to remember liking it in the theater more than at home. It's kind of a "see it once" type of thing, whereas the TV episodes I can watch over and over again and never get tired of. YMMV, but it sort of came in short of what I'd hoped it would be.
(OTOH, the extras were almost funnier than the movie itself, and it was neat to see the faces behind the voices...)