I can live with it. I liked that each Marvel Studios movie had its own sound, and continuing that with "The Avengers" was equally important to me because as a meshing of characters we already know, the sound that unified them had to be new. It couldn't play favorites toward one of the team members.
I like Silvestri's style more for a Captain America solo movie- heroic, uncomplicated, old-fashioned, action-centric, brassy, loud. What The Avengers will sound like will be interesting, I certainly hope they don't make it overly "modern." What this DOES mean is that the score will feature a continuation of Captain America's theme.
But damn, his hero themes are like nothing you've heard. Other than maybe Williams, Goldsmith, or Elfman, who better to score a superhero movie?