There have been people advocating that for a long long time. Almost a little shocking to see Roddick as the voice of reason there!
Aside from the mental aspects ("losing a volley" LOL), which I absolutely agree with, I would also worry about the streakiness of the serve. I have the feeling that typical serving strategy may spread out the penalties from double faulting/losing a rally. I would worry that, with 2 first serves, while one may win many games very convincingly, one would also toss away more games....and that would be a very poor trade-off in a sport where games are tallied!