I know that's not true for every viewer, but I really didn't recall all the ins and outs of how Tony Stark became Iron Man and thus didn't know what would happen next.
I had to check Wikipedia when I got home in fact for the reminder that he was in Vietnam in the early '60s as a U.S. advisor.
The story is updated to Afghanistan for the new movie, and it makes it seem immediate and intense, and since we spend the bulk of the movie with Robert Downey Jr. and not the Iron Man suit, it makes the story seem all the more human, a film not a movie, a richly textured graphic novel on celluloid, not just a comic book splashed on the silver screen.
When we get to the action sequences, which are plentiful, they are wonderful exclamation points to a story-driven adventure. Sure there are some obvious markers. Canny viewers will at least suspect the underlying conspiracy and even detect the inevitable mano-a-mano, but that's really OK. It didn't matter that we all knew Spidey and Green Goblin were going to have to kick each other's butts before the final real either.
Speaking of the final mano-a-mano, it of course had to be Iron Man against a bigger and stronger man-tank, right? It works in cool ways and is far more than the model kit vs. model kit extravaganza you might expect.
In summation, Iron Man is a pleasant surprise, the most fun I've had at the movies since the last time I went to a good movie. I saw it in digital with surround sound or some sort of stereo that made everything shake when stuff "blowed up real good" so it was a great theatrical experience, and a great argument for getting out of the house to see a flick.
I didn't wait for the surprise post-credits moment that suggests a mega-cool sequel--though the rumors are true. It is you know who as um hum. I figured that would be online--and it is--and my policy is still get the f out of the theater when people start stepping on my feet, but there was a great teaser for The Spirit, speaking of comic book characters whose origin stories are not as well known.
The Slate Cultural Gabfest podcast--which can be downloaded for free--includes a great discussion of Iron Man and other summer movies with some interesting contemplation on the subtext of Tony Stark's weapon's merchant change of heart.