Michael Arndt is one of the reasons I have faith in this first installment of the new trilogy. He wrote Little Miss Sunshine and Toy Story 3, both of which were very enjoyable movies. These two credits alone prove that he understands character development, something which the Prequels had none of. Also, he is of the generation that cherishes the OT and recognizes the shortcomings of the prequels (regardless of whether or not he personally enjoyed them). This combination makes him a good choice, IMO.

Since ROTJ wrapped up the series so nicely, he will have a lot of "setting up" to do, which I expect will lead to some of the grandeur of the PT in terms of understanding how the galaxy has changed since then. That being said, if he can keep the story focused and character driven, then we're already looking at a film that should be better than the PT and almost on par with the OT.