Just saw this. Honestly, I think it's okay, but I don't LOVE it like I did the first and second (not sure why the second get quite as much slack as it does). Mainly, it is WAY too long. And while I liked a lot of the Tony Stark stuff, after so long it felt too much. It's innovative use of the suits was great all around, though.
As for The Mandarin...I don't have an attachment to the character, so that didn't offend me. But the turnaround it just felt unnecessary.