I question the fact that they really haven't faced any adversity. I could see them having a really bad game at a critical point and it all falls apart.
I agree with Whit's comment....the 99 Rams are a good example: its better to face some adversity in the regular season....it gets you ready for the playoffs. The Bronco's championship teams in the late '90's had a couple of bad games before they won the Super Bowl....
Eagles look very talented, but for some reason, it seems a little 'fragile' to me... just my take.