So here's our heroine, Alison Scott (played by Katherine Heigl). She's in her mid-20s, and she's just landed a promotion to an on-air position at E! TV. While celebrating that promotion, she has a bit too much to drink and has a one-night stand with Ben (Seth Rogen), who she finds so unappealing that she cannot bring herself to touch him the next morning. Eight weeks later -- she has not seen or spoken to Ben in the meantime, or had even the slightest interest in doing so -- she discovers that she's pregnant.
So, the mystery: With that setup, how is it that we never, not once, hear the word "abortion" during this movie? Oh, one of Ben's stoner friends raises the subject, but can't bring himself to utter what he calls "the A word;" the idea is turned into a joking suggestion that Ben should encourage Alison to have a "schmaschmortion." And Alison's mother, who appears in one scene only and is clearly meant to be an unsympathetic bitch, tells Alison that she should "take care of" things. But that's all the lip service that's paid to the subject.
Now I get that a comedy about the consequences of unplanned pregnancy doesn't get very far if the woman chooses abortion, but we never even see Alison consider the idea seriously. How realistic is it that there wouldn't be some serious "hmmm.... guy I don't know and aren't attracted to, career starting to take off, I'm still young... maybe I shouldn't have this baby" thinking going on? And since we don't ever see that, Alison becomes a cipher, a mere device; she decides to have the baby solely because the plot requires her to.
And since I can't believe in Alison as an actual 21st-century woman, it's nearly impossible to care about whether she and Ben will make their relationship work. Rogen and Heigl have little chemistry, and I never once believed that they should be a couple. (Rogen loosens up considerably in his scenes with Paul Rudd, who plays Alison's brother-in-law; theirs is the most interesting relationship in the movie). Alison actually sums up her relationship with Ben at one point by saying (roughly), "I'm a nice person; you're a nice person; we're just trying to do the nice thing for each other," and she's absolutely right. They're not trying to make it work because they care about each other; they simply feel obliged to do so.
Even worse than the implausible story and the unconvincing central relationship is the fact that the movie isn't very funny. The jokes fall flat, and the secondary couple in the movie, played by Rudd and Leslie Mann, are a nasty, unhappy pair who are almost always at one another's throats. Ben's housemates are a tiresome collection of stoner cliches who exist only to be even less ambitious and responsible than Ben, providing an excuse for Alison to think, "Well, he's not that bad...".
After the tedium of The 40-Year-Old Virgin, I began to wonder if Judd Apatow was peddling the Emperor's New Clothes. I'm not wondering anymore.