I liked it for what it was. That said, I found two things obviously annoying me throughout it. 1. I believe not once was Cowabunga uttered, and 2. No really bad joke made by Splinter.
That being said, the new series makes me want to cry to what they did to some of the villains. The 80s cartoon was a far more entertaining story arc.
This, like Batman Begins, merits a few sequels with as much of the cast returning as possible. I would absolutely love to see more of the great animation, and perhaps a better story this time.