I just got back from seeing it... I... I... did not hate it. Like Transformers 4, I went in with extremely low expectations, and both it and this movie turned out decent. At worse it's a generic action movie. Inoffensive, and might be enjoyable for TMNT fans.
The real negative is the plot and editing. The movie actually could have been longer like 120 minutes long to flesh out more of the plot and action. The scenes just jump by one after another. There is a pretty complex (and stupid) plot, and I like the origin story of the turtles. There's more plot here than GOTG for sure. GOTG is much more well put together movie. The plot is bad because of how they chopped up the script in TMNT. Some of it is obviously because they cut Fitchner's role as the Shredder and had to reshoot it. The fight scenes could be longer too. Yes, I wanted more.
That said, I don't agree that the turtles don't get enough screen time. It's definitely not as turtle focused as the other 4, but they get a decent amount of screen time. Decent of course, but like I said, could definitely use more.
Megan Fox... was perfectly fine as April O'Neil. This April doing everything she can for her big scope? Why, just like the original cartoon April! She's also NOT the eye candy female that does nothing in the movie. She has a purpose, she has a motivation and contributes to the story, maybe a little too much, but you can't say she's useless. This is the best April O'Neil. There, I said it. Yeah, it's an April movie, but any failings with the character can be traced back to the script. Her acting's fine. She had some pretty funny moment with her trying to convince people what she saw. The reason it doesn't feel like she's bonded with any of the characters is because the story is so rushed. The movie just doesn't take time to build on any of the characters except for April, and even that is done clumsily.
Funnier than GOTG, but not as well put together. Yeah, it's a clusterfuck. I so regret watching the movie in 34th St theater rather than the one in Time Square. A good chunk of the climax in the movie was in Time Square.
Other thoughts. The turtles were NOT April's pets, nor did she name them. I don't even know what people were watching. The turtles were test subjects for a project called Project Renaissances. Hello, Project Renaissances, not because a 10 year old girl knew the renaissances artists. She was just a little girl playing with some animals in a lab.
Splinter was pretty badass. His origin is stupid, but... did a rat mimicking a ninja master really sound any less stupid? It really got me thinking that on my way back. Even as a kid, that part about TMNT 1 stuck out. I was more familiar with the cartoon back then. Now that I think about it, having Hamato Yoshi as Splinter really just makes more sense in the grand scheme of things.
Overall, it's a bad movie because it wasn't able to tell a coherent well developed story. A lot of little pieces within the movie are well done.