The main problem of the movie is, that it expects the viewer to feel sympathy with the choice that the female love interest of Tony Stark has to make. That the choice in itself is utterly moronic (do I let the Mandarin take over my body to reign as tyrant?) seems to have gone completely unnoticed. You could argue that it merely seems like an utterly moronic choice to a western viewpoint, but would make sense to someone from a different culture (honor the wishes of your ancestors to the point of self-abandonment).
That, though, is a useless generalization, since similar ideas have been and are still part of the western idea-space in some places and not unique to Asian cultures. That doesn’t make them less moronic, either here nor there. Another big problem is the CGI, which is used extensively in the movie, but not all that well integrated with the parts done as conventional animation. At times the movie looks not directly ugly but stitched together from parts that just don’t fit.
The plot is also pretty lackluster, side-tracking the main action (the resurrection of the Mandarin) until the movie is almost over. The choice of the Mandarin itself is problematic too, but only highlights a basic problem of Iron Man, his lack of interesting villains. A good one would have complemented the basic concept of a technology-driven futurist, either an ultra-conservative who abhors the insane pace of modern change or an ultra-technologist against whom Stark would have looked sane.
But the Mandarin is neither. Just an artifact from the cold war, which makes for a decidedly boring villain. Maybe that was the reason they only let him appear once the movie was nearly finished. Invincible Iron Man isn’t awful by any means, just pretty dull.