With this cast, this director (Greg Mottola from Adventureland and Superbad)and an interesting concept this should have been, at the very least, a great comedy. Sadly, it disappoints. It's only funny in small non-sustained stretches and the comedy potential of a rude, pop culture obsessed alien is mostly wasted. Most of his humor is way to obvious pop culture references (how many tie ins can you you have to E.T. and Close Encounters of the Third Kind) and blatantly telegraphed. The core story of Simon Pegg and Nick Frost taking a road trip is the most interesting but it often feels as if the film is vacillating between the raunchy comedy of Superbad and the more straight forward storytelling of Adventureland without ever choosing a consistent approach. One second Paul is dropping f-bombs and showing his ass out the window the next he is a selfless life saver with no real character exploration given to explain his random life changes.
Its odd to say - especially based on the Paul centric advertising - but the human story here is far more interesting than anything Paul brings to the table.