I really like Kaplan's design for the Vulcan students' costumes seen near the beginning of the film. They're striking and alien yet not alien enough to seem out of place.
Kaplan's design for Spock's mother, Amanda, definitely feels like it belongs in the same world as the Vulcan student designs. It features the same long, body shape but it is feminized with a flowing scarf and with warm colours.
Kaplan's designs for Spock are simple and appropriate. They don't draw attention away from Nimoy's performance but they're "sci-fi" enough to be memorable.
Aside from the new Starfleet uniforms, probably the most memorable of Kaplan's costumes for this film is Spock Prime's parka. It's a beautiful costume. One of them has toured North America as part of the recent traveling Star Trek exhibits. Another was sold at the recent Julian's Star Trek auction.
Kaplan also created a host of Vulcan costumes for the extras who performed as scientists and engineers building the Jellyfish ship, the Vulcan elders from the Katric Ark and the council from the Vulcan Science Academy. Some of these, notably the female costumes, share similarities with the collars of the Vulcan student costumes. A few of these costumes have also toured around the United States to help promote the film.
Overall, I think Kaplan did a great job costuming Abrams' film. Collectors will be very excited when more of his costumes become available for sale someday.
More information about Kaplan's work can be found in Mark Cotta Vaz's book, Star Trek: The Art of the Film.