To be honest, I dislike the new animation style (16 year old Ben actually looks younger and looks more like a bad boy, compared to the original version in Alien Force and Ultimate Alien, not to mention the clearly different attitude) and some of the alien redesigns are just plain bad. I also really dislike 16 year old Gwen's new looks in Omniverse, and when she returns again, my God she's even more horrible. And that new Anodite form looks...stupid. Anodites don't wear costume. I'm fine with something that looks like a natural clothing, but that's a costume, not a natural clothing. Kevin's new design is also a bad one. Seriously, why can't they just keep the old designs?
And no female main character? What about Julie? Heck I'd even accept that seemingly random young female Kineceleran that has appeared twice so far as a female main character.
Also, too bad they just can't make it so that Azmuth finally decides to install the Ultimate feature on the new Omnitrix. I actually like that feature, a few aliens actually looks better when they go Ultimate. Echo Echo and Wildmutt are good examples.

For alien redesign, the ones I dislike are:

- Humongousaur, that belt just looks so unnatural
- Spidermonkey for the same reason
- Big Chill, what the hell, he went from a cool (pun intended) moth man into a this huge gorilla-like guy with bat-like wings. I saw people being happy because he's now actually "big", but that's just stupid, based on his old appearance I doubt "big" here is meant to refer to size, rather it must be referring to temperature. "Big Chill" as in "extremely cold".
- Echo Echo. That more blocky head just looks too odd. And they changed Dwayne's favorite design. After his death.
- Alien X. IMO, this is the most ridiculous redesign. Comical big chin works for Diamondhead, not for the "cool and mysterious" godly omnipotent being like Alien X.
- Four Arms. Mainly because of that a moustache?
- Clockwork. Also mainly because of the head, it looks too flat and it's stupid. And that oddly shaped "window" on the chest, what's wrong with a circle.

Those are the only ones so far that I've seen AND dislike.