Saw it in IMAX 3D. I thought Ultron was pretty cool, and there was some decent action sequences. I was also pretty excited to finally see The Vision on the big screen, I've been waiting for this. He rocked. Overall opinion: A fun outing, interesting in spots, but it never really rises out of the genre. Winter Soldier had more depth.
The more intriguing ideas were touched on but not really dug into. For example, Ultron is Stark's child, so what makes Ultron much different from Stark? (There's even a line that suggests this -- that Ultron gets confused between creation and destruction, but where do you think he gets it from?) I really really wish they had dug more into that. Every time the movie started asking those uncomfortable questions, it ended up getting back to an action sequences. (Same thing with the intragroup skirmish at Stark's place; Thor shows up as a deux es machine, versus it being solved organically.)
In this movie, I also had a much deeper feeling of "What makes the Avengers any better than the guys who trash the place, since they are also trashing the place?" The biggest sense of this is when
The most WTF moment that I understood why they did it for characterization but that is likely to never happen is when
Anyway, for people who don't plan to see it but want to know how it pans out (body count and the Avengers 3 roster):
Also, the "sneak peak / end clip" that shows up in each Marvel movie: