Why this film doesn't work
The problem with this film is the overall premise: we're to believe that Katherine Heigl would be remotely interested in Seth Rogan. It just doesn't work.
I'm not just talking about looks either. It goes beyond that. This film doesn't establish a believable rapport between them from the beginning; one where we can understand why this chick, who can get almost any man she wants, would go for somebody as boring, lame, unkempt, unaccomplished like Rogan. He bought her a couple of beers. And now suddenly she decides she wants to spend the evening alone (!!!) with him? Nope. This type of BS just doesn't work, and it damages the film, because it lingers on throughout the entire running time.
If the premise doesn't seem plausible, everything that comes after it is worthless. I'm not stating that it's impossible that Heigl would go for Rogan. What I am stating is that this film failed to establish any reason(s) for her to. And that's ultimately why this doesn't work.
Of course gorgeous women date average looking to ugly men all the time. And of course these men aren't millionaires a lot of the time. But they all have something attractive about them to the woman in question: charisma, humor, intelligence, creativity, etc.
Rogan doesn't have any of this throughout the entire film. We don't see any of this. It can be argued that he is sortof charming, maybe sortof charismatic. Maybe. Sometimes.
But this is just not enough to connect with the audience and remove it from their minds.
I personally know beautiful women who have been attracted to relatively ugly men. But these men all had something interesting/intriguing about them that was attractive.
In this film, Rogan is just some goofy nobody -- especially at the all-important beginning, where the idea is to attract this beautiful woman into your world in the first place.
It started off okay, with him buying her the 2 beers. But it went downhill from there. The people writing films like this just don't understand women. I don't know any woman who's watched this film and found it believe that Heigl would spend the night with Rogan.
And most guys probably don't find it believable either.