Okay, here are my thoughts:
Megan O'Neil: I was rather surprised that Fox actually wasn't that bad. Her acting isn't top notch or Oscar-worthy, but she really was trying and I have to give her credit for that. I just disliked the fact that she was basically the heroine of the movie, and so much emphasis was placed on the fact that she was the one who saved the turtles. Even Splinter basically regards her as some kind of guardian angel, or savior-like spirit. It just felt really out of place. And although April has more to do in this movie as oppose to previous incarnations, she is still so totally the damsel in distress, like ridiculously so.
The Turtles: Freakin spot-on. I loved this film's turtles. Their personalities are amazingly canon and I actually really like their new designs. However, I so wish this film focused more on the turtles than April, but that was expected I guess.
The Villains: One word: no. These villains were so ridiculously cliched. Why the heck wasn't this Eric Sachs just plain ole Baxter Stockman? Oh yeah...rewrites. And Shredder? No backstory, no mention of Oroko Saki, no real sense of threat to be honest. I have to say it, the 90s Shredder was AWESOME compared to this new version. That one had real motivation, manipulated kids and teenagers to thwart out his schemes, and had a personal vendetta against Splinter and the turtles. This one: nothing, except for a crazy mech suit. Meh.
Splinter: Dammit, I hate to be the bad guy here, but I really didn't like this Splinter. He was extremely too harsh on his sons (like abusively so), lacked real wisdom and although he was protective over the turtles, he just didn't seem very father-like. And he learned karate from a book...seriously?
Overall, it was okay. I wouldn't have minded a longer movie with more fleshed out characters and a much better storyline, but I do hope there's room for redemption in a sequel. And for the love of God, ditch Vernon and bring on Casey. 5/10