Tony Stark is in many ways a changed man. Yes he his still glib and suave but once the spotlight is off he shows a more vulnerable persona. The fact that he spends more time out of the suit than it shows how much he has been traumatized by the events of The Avengers and the attack of the terrorist, Mandarin.
Robert Downey Jr really shines here playing it both loose and tense as he shows how Stark finds this reserve of character and steadfastness to do what is necessary to save those he loves.
Iron Man 3 is quintessential Shane Black - full of dark humor and unexpected twists. He loves to subvert your expectations in a way that will have you alternating laughter with sounds of amazement.
The action builds to a number of amazing set pieces - the monkey-in-a-barrel sequences, the denouement when Tony Stark/Iron Man confronts the villain had me holding my breath at many points.
After having been subjected to bad-to-middling special effects in a number of recent movies, I had a hard time telling what was real and what was CGI. The effects were that good. I watched the 2D version so I can't comment on the 3D transfer.
I have to give kudos to the entire cast. Gwyneth Paltrow finds added dimensions to Pepper. Don Cheadle as Rhodey is hilarious in the way he and Downey Jr. play off one another. Guy Pearce is like a snake - both mesmerizing and repellant. Ben Kingsley as the Mandarin gave the movie one of it's best twists!
James Badge Dale and Rebecca Hall are great as well. It's also good to see Jon Favreau back as Happy Hogan.
A lot of the times the third movie in a huge franchise is content to rest on its laurels resulting in a tepid film that pales in comparison to what came before. Iron Man 3 subverts this expectation, giving us a thrilling ride but also taking the time to explore characters.