I've seen it twice. My initial reaction was fairly positive. I thought it hit some good notes and was a lot of fun. Good performances from Quinto as Spock and Urban as McCoy in particular.
Second time around I became aware of how insanely fast-paced this thing is, and somewhat shallow. While it touches a lot of familiar Trek places, there isn't a lot of depth to it. And surely something as epic as the Vulcan sub-plot needed a bit more time to be dealth with.