It's very similar to "Knocked Up," the other Katerine Heigl I've seen, but I would say it was better. It's better for a couple of reasons. Firstly I suspect it was funnier (though some people might argue there's a bit of "potty mouth" humour about it). Secondly, and with the greatest respect to Seth Rogan, I could actually see her falling for Gerard Butler. Both were slobby, sure, but Butler's character had more about him than Rogan's character did.
So all in all it's a pretty good film. It'll never win any Oscars, but it was still pretty good.