I didn't read Iron Man as a kid, so I can't say I'm invested enough in the characters to even possibly get upset at who's playing whom and all that... but I admit to not really seeing Scarlett Johansson as Black Widow. But who knows? Definitely a must see movie for me, even if Black Widow was being played by Betty White (especially if?).
And I guess the Mickey Rourke character is some sort of amalgam of Blacklash/Whiplash and Crimson Dynamo? I'm pretty sure Blacklash wasn't Russian.