Really, really good. Go see it.
This is one of the most approachable of the Star Trek series. You could go in with no knowledge of Star Trek and enjoy it (CupcakeGirl is a good example.. she said she liked it). Very action oriented, much more of a "realistic" feel (some things I liked, there was actually things like military discipline on the ships, the tech level felt more believable (engine room, bridge), fights seemed realer (bodies, vacuum)) and was quite a fun night.
I watched this on IMAX, but the theater was so full by the time we got there so we were way up front. I really hate how we Americans fill in a theater, even when it was packed. So much lying (I am saving that seat = my fat ass doesn't want anyone sitting next to me.... I did look back at least once or twice and saw that a number of those "saved" seats were empty... why was I not surprised).
PS, J.J. Abrams, you are officially banned from the lens flare effect... are you kidding me? You just used up a lifetime pass, something like 200+ uses...