1. At some point, a character will be talking on the phone and be greeted by a Brad Bird voice cameo.
2. Jeremy Renner reveals that his secret is that he is actually Hawkeye.
3. Plenty of screen time for Simon Pegg, Renner, and Josh Holloway, who's been mostly left out of these first trailers.
4. (Least likely) The trailers don't give away all the best parts of the movie.