To paraphrase the great philosopher Carlos Mencia, boys tend to prefer movies full of action and out-of-this-world things that they can't encounter in their own lives. Girls, on the other hand, usually prefer realistic movies full of easily relatable situations. Of course there are exceptions in both cases, but for the majority, it tends to be true.
Anyways, I thought it was pretty good, as did everyone I saw it with (mostly girls).
It seems as though I'm the only person I've talked to that actually liked Michael Cera's character (Forgot the character's name; the one that was gonna be the adoptive father of the baby). Everyone said the reason they didn't like him was because he left his wife to try and be with Juno or something... but I didn't pick up on that, I guess. I thought he was just leaving his wife and coincidentally liked Juno as a friend - nothing more.
Hooray for obliviousness.