The most common complaint I've heard about Evens (although not in this thread) is that he's "Too skinny".
For those with that opinion, I direct you to
this article. Scroll down to the 2nd photo.
It isn't that he is skinny, though some may not be able to articulate it any other way, but rather he has a lean, lanky, swimmer/footballer(soccer) build much like Brandon Routh, Ryan Reynolds, etc. His face is also boyish and not at particularly like the square-jawed all-American Quarterback 1940s ideal he is so often drawn as(Some longer hair might help, but his face just doesn't read 'Captain America' IMO). These aren't criticisms, just observations.
I think Evans is a tremendous talent when he has a role that suits him and writing to back him up, but I don't think he looks anything like Captain America and he seems like a 'safe' choice after some of the more 'out-there', but potentially far better names we heard along the way. Won't hurt my enjoyment of the movie if it is otherwise good, and they could have done a lot worse, but he won't be replacing my image of cap either way.