a bunch of people have written about the politics of juno.
juno is just another example of something that hollywood has been doing for more than a decade. almost every time that someone gets pregnant in TV or movies, the same basic thing happens: the knocked-up woman asserts her right to choose and then chooses to have the baby.
it's a time-honored cop-out, designed to throw a bone to both sides of a contentious issue. and, to some extent, i don't blame them. while there are movies that want to address the abortion issue, a lot of films want to do something else. so they take the path that avoids the distraction of an abortion-related controversy.
if you're so inclined, you can see juno as a pro-choice movie or as a pro-life one. while the issue is overtly present in the film, its not a film that is primarily concerned with that issue.
i also thought it was very very good. so go see it.