Well I would like to begin by declaring my immediate bias. I love Marvel Comics. Every single damn comic book character published by those wonderful creative masterminds gets me harder than a sexually aroused Ben Grimm. I'm also obsessed with open ended super hero games where you can fly, jump really high, web-sling, etc.
That being said, this demo was pretty good. The setting is the middle of the desert, some top secret military base. Reminded me of The Incredible Hulk: Ultimate Destruction (Pretty fun sandbox marvel hero game where every other level is some top secret military base in the middle of the goddamn Mojave). The flight system is pretty fun, albeit loose considering the default camera sensitivity is so high you feel like a 10 year old off his ritalin wearing a jetpack. You get used to the controls eventually and let me tell you- dodging missiles in mid-air is pretty dang enjoyable.
The graphics are beautiful with a definite attention to detail. Being a demo, there were a few buggy areas graphically where it seemed unfinished but I'm hoping those will be polished out in the final game. There is an upgrade system with your armor, giving it just that HINT of RPG. The weapons are fun to use; you dont really feel like Iron Man until you've shot a volley of rockets at a helicopter while speeding through the sky. The melee punching gives you a sense of power as well, and you can actually rip the tops off of tanks by rapidly tapping B (melee button). The targeting system is neat because it is useful but at the same time it doesn't "baby-up" the difficulty of the game.
All in all, the demo showed definite potential. Wasn't "rock your balls off" exciting but I certainly enjoyed it. Sometimes licensed super-hero games have been known to show promise but FAIL HARD in the final production (COUGH SUPERMAN RETURNS COUGH) but then again don't all licensed games? (with the exception of such gems as King Kong and IMHO Spiderman 2) The gameplay is solid and playing as Iron Man is badass enough, so really I see the game only being able to go up from here.

-Tusken