He only has two lines in the the teaser and you can't draw much from them. On the other hand, everything else about this movie jumps off the screen, jamming every bit of action they can into thirty seconds while giving some bold impressions of Steve Rogers' personality both before and after the procedure: His courage, willing to keep going in spite of his limitations and frailty (his struggle to survive boot camp training, the nervous look on his face before taking part in an experimental procedure) and his courage in the face of danger, charging onto the battlefield in full Captain America regalia. I think his frailty jumped out at me not so much because it looked unnatural as it was just jarring to see Evans so small, so sickly, appearing shorter than Peggy Carter in the first shot. Stanley Tucci's dialogue as Esrkine sounds very much like a mentor, warning him of the dangers and making sure Steve is taking part in this procedure for the right reasons: 'Not just a soldier, but a good man.' Visually, this trailer is stunning. Johnston manages to meld the practical technology, equipment and costumes of the World War 2 era (the prison camp clip with Steve, Bucky and the Howling Commandos walking out the front gate armed to the teeth) with the sleek technology and weaponry of Hydra (the brief shot inside the one-man submersible,the flame-throwing soldiers surrounding Steve and what looks like a precursor to the stealth bomber flying over the battlefield). The Hydra technology seems extremely advanced without feeling outlandish, it's still with in reason. Johnston's timing for action and choreography in this clip is top notch. At this point, the acting performances from the cast are the only thing left to seal the deal on this one.
P.S. I want anyone reading this to go out and do a survey for me: What era does Captain America take place in? (I'm betting you'll be surprised by the responses)