I'm pretty sure I'm in the minority opinion here, but every time I re-watch AoU I like it even more. Really solid action, and Ultron has grown on me quite a bit, and I even liked him coming out of the theater for the first time. I dunno, I thought it was a damn good installment personally. It's possible I'm untainted by comic representations of Ultron, as I've never seen him depicted, other than simply knowing of his existence from owning all the Marvel trading cards when I was a kid. But I thought they did a really good job of depicting him as an AI based somewhat off of Tony's personality. I crack up at the end when Hulk leaps into the plane or w/e those things are that Ultron is using to fly away from the flying island, and you just hear Ultron say "oh for the love of..."
It also might help that I have a man-crush on James Spader ever since Boston Legal.
-edit- To add some on-topic stuff: This just keeps looking more and more amazing each trailer/teaser. I will probably have to stop watching them if any more get released. I just can't even.