This movie isn't actually that bad; it certainly doesn't deserve the endless line of 1-star reviews. I went to see it with very, very low expectations, after reading a negative review of it, and ended up enjoying quite a bit of it.
Even from the trailer you can tell this is a silly, childish comedy with plenty of toilet and/or sexual humor. I don't know what people came to expect from it - this certainly doesn't attempt to be anything else besides that. Maybe many people aren't used to seeing De Niro in such a role, but hey, he's done other silly comedies already. Not all the jokes are that great, but it was good fun nevertheless.
So, definitely childish, definitely silly, but also definitely funny in my book. I even ended up feeling for De Niro's character - hey, it's his last stand after all. So, if you don't expect much and aren't easily offended by jokes that sometimes are a bit too silly / gross /etc, you might even enjoy this!
