I thought Chris nailed it. He was Steve Rogers to me, can't wait to see more from him.
If I have a complaint, and it's a small one, it was that they didn't alter Skinny Steve's voice at all. Hearing Chris' deep voice coming from that skinny little dude was a bit distracting to me.
Yeah, I was a little surprised by that as well.
While we were watching the movie, my wife leaned over and made a comment about it, too. The voice just didn't quite match the body. Not a big deal, though.
I'm going to have to disagree with you guys on this one. I didn't see it as a big deal at all. In fact, I think it would have been a lot more distracting if they HAD changed his voice post-transformation. Not only would it have seemed a bit more cartoon-y, but it would have made it seem more like Steve became a different person after being administered the Super Soldier Serum.
One of the big themes of the movie - indeed, one of its strongest points - is the idea that Steve had it inside him to be Captain America the whole time - he had the guts, the intelligence, the selflessly heroic nature, the only thing he didn't have was the physical strength. Therefore, after his transformation, it seems like we're finally seeing "the missing piece of the puzzle" - Steve getting the last thing he needed to be a hero.
If they'd changed Cap's voice post-transformation, I think you would have had a lot more people laughing and poking fun at it. Remember in
Revenge of the Sith after they finally put the Darth Vader mask on Anakin Skywalker and he suddenly sounds like James Earl Jones (or when the same thing happens to Dark Helmet in
Spaceballs)? I think changing Cap's voice would have had exactly that effect from the perspective of the audience. Better to not change it at all, as it underscores the congruence of pre-serum and post-serum Steve.
Besides:
1) It is possible for skinny guys to have deep voices
2) Chris's voice wasn't even that deep. I mean, it was authoritative and commanding, but it wasn't Barry White deep, which certainly would have sounded ridiculous. I thought his voice was just right for Steve Rogers/Captain America, and I wouldn't have changed a thing about it pre- or post-transformation.