Well, Pryor did manage to run all over that Indy defense and Kaep is playing at home, and so far KC is the top ranked D against opposing QB's. But right now I'd have a hard time not starting Vick. #3 ranked QB overall in standard scoring and the only way Philly has a chance of winning any games is if that offense continues to roll. Philly is going to be in shootouts all season long and with the way Chip Kelly is running that offense they are going to continue to run a huge number of plays which increases Vick's scoring possibility by sheer quantity of chances.
Basically unless you think that Kelly's offense is unsustainable and/or you think Vick is going to end up hurt, I think you keep running him out there like you would any other stud QB.
(Personally, I think that offense bogs down as the season goes on due to conditioning/injury and defensive coordinators getting tape, and I would look to package Vick in a blockbuster trade basically selling while his value is high).