I just finished watching it about 20 minutes ago, and I loved every second of it. The fact that so many characters appeared in this special was too good to be true, and it kinda shows since the '87 verse was only briefly visited and supporting characters like both Aprils, Casey, and 87 Splinter only got cameos. still, I appreciate how all of them had a chance to showcase.
Utrom Shredder was at his craziest here, trying to take down the universes, even if it meant he'd be wiped out too. I loved that montage of alternate Turtle-verses, and the shot with the Live-Action Turtles had me giggling. They looks o out of place compared to the rest of the multi-verse.
I do wish we got to see more of Uncle Phil and Krang actually doing villainous stuff. It seems once Utrom Shredder and Karai showed up, those two were benched and remained inactive until the final battle. Hun becoming an old villain is all kinds of awesome though. I didn't even notice the movie villains until others pointed them out.
As for all the jokes at the expense of the '87 show, I got a laugh out of them. The whole setup of the movie is pretty serious and fatalistic, so its nice to have someone bringing on the jokes. Raph breaking the 4th wall and Hun getting confused each time never failed to make me laugh. Mikey and Raph getting attached to the cast of the 2 other universes was also great, even though the Mirage Turtles were far too hardcore even for Raph.
So even though they're the good guys, the Turtles didn't actually defeat the Shredder. Karai managed to save them from nonexistence, Hun gave them the technology to track down the Technodrome and Bebop and Rocksteady were the ones who wiped out Utrom Shredder. It's different but a great way to show they're not nearly the monsters that U. Shredder is.
All in all, a great film, and a fitting send-off to the 25 years of TMNT before starting anew as a Viacom property. This is probably the greatest thing to air on CW4kids, and I'm glad I was there to witness it.