I enjoyed it. It was an entertaining movie that doesn't try to be anything else. It wasn't pretentious with a message or any crap like that. You walk in expecting to see in a robo-suit fight some bad guys, that's exactly what you get. But while it wasn't some pretentious attempt at being artistic, it also wasn't mindless and pandering to idiots. The proper way a pop-corn flick should be.
It's as good as the first Iron Man, and better than the secoond, which in all honsety just felt like a two hour trailer for The Avengers.
The movie had some great one-liners, and Ben Kingsley's character ends up being hilarious as the movie goes on. It was good to see they managed to have a kid befriend Tony Stark without being annoying, or more accurately his annoying traits were actually an intended part of the character. Still, "dads leave, don't be a pussy about it" was an awesome line. Mind you, I never once believed that Pepper was actually killed.
On the complaint end, it didn't really feel to organically fit with the other two the way those two fit together, or other movie trilogies do. But I'm of two minds on that. It can be a bit irritating, but then it probably best to make these movies as stand alone as possible, especially given it and all the other Marvel movies aside from the Spider-Man and X-Men series are all interconnected and part of the same continuity.