My first and still present thought is that they should've released a single portable system that plays GCN games as well as GBA games... basically a GameCube / GameBoy Player in one portable system. Instead they come up with this. I'm not sure what to make of it, but Nintendo has certainly earned the right for me to give them the benefit of the doubt.
It definitely has some valid uses in sports and strategy/RPG's. Think about playing Madden... one screen has the main gameplay screen and the other has the play calling / audibles / stats on it. In an RPG one has the overview of the world with inventory screen and the other has the current battle or something like that.
I'm interested to see if developers other than Nintendo actually support this though.