Saw it in 3D this morning and it was very good. Compared to the other first solo films, it was clearly better than Thor and Hulk, not as good as Iron Man and Captain America, and probably on par with Ant-Man.
Cumberbatch was really good. The Stark and Iron Man comparisons are overblown. This movie and his character stand out. His American accent wasn't as unnerving as I expected (for example, I find Hayley Atwell's American accent quite strange). About halfway through, I realized it's because Cumberbatch sounded very much like an American actor who would have been good in this role about 20 years ago. Don't want to color anybody's perception, but I'm curious if anyone agrees. PM or rep me if you think you know who I'm talking about.
Definitely stay through the credits. Both do a good job of setting up Phases 3 and 4. I think the first one may be a scene from a future film similar to the Ant-Man post-credits scene from Civil War.