I'll say yes, which I find to be profoundly disturbing. Far too much emphasis placed on one aspect of an otherwise solid movie that did so many things right. Rhodes has never been portrayed better, for example; he went from practically being a nagging ex-girlfriend in both of the previous movies to the bad-ass military man that he should have been from the start. He also finally acted like a friend to Tony this time instead of a foil.
That's just one example of many, but getting back to the matter at hand, it's obvious by people's own words. On several occasions, many have outright said that the twist ruined the villain and the movie for them. Others haven't stated as much, but I get the feeling that many of the criticisms you see from certain folks seem to spiral out from the Mandarin twist, and fall into the category of nitpicks more than anything else. I'm the same way in a lot of cases myself, as when a movie loses you, all you tend to notice are the negatives. Still, I'd say that the degree to which most of the common grievances affect the movie is minimal, i.e. the kid, the mansion attack, pepper offing the villain, etc.