Bradley Cooper really does make the movie work.  Especially when he's pogoing between manic super-genius and thick-headed loser.  Though the main opponent manages to both be super-smart at setting up Cooper's character and super-sloppy in other ways.  Like leaving two random good samartian types lying stabbed to death in the park...
Also I kind of don't buy that the loan shark will just decide to take some random unidentified pill dropped by the dude he's shaking down for a payment...
Still the movie is basically enjoyable.  Once again, mostly because of Cooper...