The thing about this film is that it's more of a "dramedy" than a straight up comedy. The people that don't enjoy it are those that are expecting it to be another 'Knocked Up' or 'The 40 Year Old Virgin', but it's a more serious film than those two.
I liked it when i saw it at the cinema, but i loved it when i watched it a few months later on Blu Ray. It seemed more enjoyable when you know what to expect. It's got by far the strongest storyline of the Judd Apatow films, and Adam Sandler's acting is actually really, really good.