Same here, gerbick, except that when I first heard of Downey being considered I thought, "whoa... he should be just the one to understand the character."

And like you, I found myself about 2/3 of the way through the movie so caught up in his performance that I came to thinking of him as Stark. I doubt anyone could have done a better job. Makes me wonder who they'll get when Downey is too old for the role...