I didn't grow up with the Turtle toys, but I watched some of the cartoons and movies growing up, so while I'm not a devout fan, I do have a fair grounding in TMNT.
Overall, I was fearful of what the combination of Bay and Fox would create...and I wasn't disappointed. It was chaos-filled a thrill ride for sure, unfortunately one that seemed to try to keep one foot in the lighthearted comics and cartoons, and the other borrowing the darkness of Nolan's sewers and alleys, without deciding which to follow. This disparity was jarring for me at times.
The cinematography was pretty dark overall, even accepting that much of it takes place in the requisite sewers. However, even the bright rooms felt claustrophobic to me. The film may have lacked the blood and gore of recent films, but it couldn't seem to shake the darkness.
William Fitchner is always enjoyable to watch, but it didn't feel like he was really stretching here, and the rest of the cast felt...well, two dimensional, in their deliveries. I had a hard time really getting worked up about any of them. Any one of them could have been hit by a truck and I wouldn't really have missed them.
The chases and crashes were fairly consistent in their ignorance of the laws of physics, which is sort of expected when you adapt a cartoon...but then the occasional slow-motion bit would be straight out of a textbook...creating further jarring for me. Entertaining? Absolutely.
Overall, it was about what you would expect from a Michael Bay/Megan Fox film. Plenty of action, not so much with the acting, a passable summertime popcorn flick for either people who grew up with the Turtles, or slightly older kids of today. If you liked the previous incarnations, you'll likely enjoy this one, but if you're looking for anything that will stimulate your brain...keep looking.