I think the cast did a fantastic job with their characters especially Urban, his Dr. McCoy stole almost every scene he was in. Great fun, only a few small flubs as far as story line but they're not critical to the success of the movie. I've scene it twice now, my kids once, we all liked it even better than Wolverine, now just waiting for Transformers 2.
I had heard that the producers struggled to get the PG-13 rating and now I know why. You'll definitely have to cover the ears of any little ones frequently, but other than that it's a really good show. I like the plot [including the twist] and the portrayals of the main characters. There were only 1 or 2 moments that dragged out a little too far so overall I'd say it was worth the money.
We took a group of 5 (11yrs-13yrs) to see Panda for my oldest son's birthday and everybody loved it. Plenty of laughs, good message, great time. We highly recommend it.