well, I can understand the thread starter's feelings.
I'll admit that I sometimes refuse to watch a movie or project that involves a particular director or actor ( actress ). In my case, I'm more conservative in my views, so if a particular celebrity is extremely liberal ( and makes really outlandish remarks ), or else does something extremely sordid or offensive in behaviour, then I will usually "boycott" that celebrity's movies.
In Downey Jr.'s case, though, it seems that he has actually cleaned up his life. I think that will bring an interesting dimension to his portrayal of Stark, as he has something in common with the character. Plus, Downey is not the typical tall, buff, male hero that is usually cast in the male hero role. I find that refreshing, as I am short in stature.
So, for me, Downey's past personal life will not affect my seeing Iron Man.
However, if one just can't stand him as an actor, then I certainly understand. There's no point in spending your money watching someone you can't stand............