I liked Star Trek 2009, but it's very apparent the writers didn't know much of anything about the Star Trek universe. The catalyst of the story doesn't even follow the rules from the franchise. This can be overlooked because the movie is entertaining as hell.
Watching Into Darkness I kept asking "Why?" over and over and never got answers. The plot falls apart under scrutiny. That's not to say it wasn't entertaining as well, but far from great. Abrams' direction is great. I think what problem there is is the fault of the writers who are attached, namely Damon Lindelof, whose addition to the writing credits of Into Darkness could definitely be seen. I'm so glad this guy isn't attached to SW7 yet and hopefully never will be.
If Arndt ends up penning the final draft I just hope he doesn't make SW7 a live action Pixar movie. Brad Bird turned Mission: Impossible into a cartoonish comedy forgetting he was working with people.