Will Farrel and Rachel McAdams among others. It's Blades of Glory but with a singing contest show. If you haven't seen Blade of Glory, this will probably be funny and stuff. But for those of us that have, well, we've seen this one before and so the lack of new material is disappointing. They even managed to make Rachel unattractive. If you've seen Blade of Glory, don't bother.
I will add that most of WF's new stuff isn't funny to me any more. Same material and characters over and over with a different skin. So, there's that that affects my perception of the movie as well.