I feel like I heard very little about this movie, but it had this underground buzz about it, which made me tape it and want to watch it. I was certainly very pleasantly surprised by the movie. In the few previews I did see, its seemed as is the preview makers were trying their best to capitalize off of the presence and screen power of Steve Carell. While he's in the movie, he's certainly not the only thing worth watching.
The story in brief is that a little girl gets to participate in the Little Miss Sunshine beauty pageant, and the trip that her family makes to get her there. Of course, there are bumps along the way, and other such hardships. But eventually she makes it to the show, and does her own unique performance (that she's been practicing with grandpa).
For me, what really made this movie so enjoyable was the dialog, and the character development. The movie was easy going, but at the same time was able to convey the realism of life, in that just because you want to do something, to get there can be very difficult and hard sometimes. Carell is wonderful in the movie, but I think the real star is the little girl Abigail Breslin who is basically the lead. She is wonderful and very lovable in a quirky girl kinda way.
My final recommendation - definitely worth watching. At this point you'll probably have to rent it, but if you wait another 6-12 months it will probably be on cable!