I'm a fan of David O'Russel, so I was damn pleased here too.
The cast and music were especially prime choices. The film is based in the 70s, so expect nothing but awesome funk and classic rock. And also, taking the leads are Christian Bale, Amy Adams, Jennifer Lawrence, Jeremy Renner, Bradley Cooper, and Louis CK..... Or otherwise: Batman, Lois Lane, Mystique, Hawkeye, soon to be Rocket Raccoon, and Legendary Comedian.
A lot of people mark this as a full comedy, and while it has its funny moments (very funny even), I think more than anything it's just telling an entertaining story about con men, gangsters, politicians, and the FBI in an amusing and complicated game. It's a bit slow to warm up, and I'm not sure how grand the pay-off is (say, in comparison to the Ocean's 11 scam being the top of its class), but it's a fine film with great characters playing will amongst each other.