Finally saw it at the dollar theater. I was fun, but I still hate the design decisions. The Turtles work better for me as smaller, more lithe ninjas... instead of huge hulking bulletproof beasts. And I think the choice to do them that way was rooted entirely in the direction they took the Foot Clan. Instead of making the Foot a clan of outlaw ninjas, they made them your run of the mill terrorist organization. They could have been the generic para-military stand-ins for the League of Assassins in The Dark Knight Rises(as opposed to the full fledged ninja clan LOA of Batman Begins), or any number of stereotypical terrorists. Complete with Arab keffiya scarves! Which is complete nonsense for a Japanese criminal ninja clan, especially and most blatantly on Karai. So, instead of martial artists with traditional bladed weapons, you had a bunch of assault rifle wielding terrorists dubbed "the Foot Clan" which necessitated monstrous turtles whose shells were basically kevlar vests. And as a result, we also got Robo-Shredder.
And I think you can tell the shift from Eric Sacks as the Shredder to nameless Japanese Shredder was pretty late in the game. Oroku Saki went unnamed, and got zero character development or really any meaningful screen time. He was a boss fight, nothing more.
I was entertained, but I just do not like those particular choices. I think it would work better as a full blown ninja movie and less of a sci-fi action/adventure. I would have saved the more sci-fi/sci-fantasy elements for a sequel using Utroms/Krang in revealed the source of the mutagen.