Abrams was essentially a hired gun on the Trek films. On Star Wars, he was as well, but clearly he has more interest in the material and has taken it upon himself to do rewrites (of a Michael Arndt script with help from Lawrence Kasdan - not too shabby group of writers there, especially in comparison with Trek). On Trek he probably didn't feel it was worth the effort to fix the scripts in the writing room, or maybe he didn't know how (or maybe even he wasn't allowed to). But he certainly fixed them when it came time to actually make the movie. Look at anything else Kurtzman and Orci have written: total shit movies. But the Abrams Trek films are for sure awesome fun times. One thing's certain: Abrams can direct an action film.
By the way, I completely agree with bkev's post.