Overall I thought it was a well-executed family-friendly action comedy. The turtles were well rendered, both in terms of their character interactions and their CGI. My negatives would be Stephen Amell's performance as Casey Jones and some aspects of the main villains. But overall, it was very entertaining and I loved the turtles, and Vern, and Baxter, and Bebop and Rocksteady were pretty good too. I think it accomplished what it set out to do.
Here is my review of the first TMNT movie in the series and some of the comics.