My thoughts on the matter:
1. I have not seen any evidence yet from Vick to make me think he's truly remorseful. Yes, he convinced the Commish to reinstate him, but if you believe that the interest and revenue Vick would bring to the NFL didn't factor heavily into the decision, then you're out of your mind.
2. That said, if Vick is truly a "changed man," it makes a lot of football sense to have him on the team:
A. Wildcat QB.
B. Familiar with the WCO.
C. Better #2 WCO QB than Todd Collins or Colt Brennan.
D. If Campbell sucks it up in 2009, we've got his replacement ready for 2010.
E. If Campbell is amazing in 2009, Vick's presence gives us significant negotiating leverage and flexibility in 2010 (i.e. we pay Jason less or can franchise and trade him to another team for a high value and already have a replacement on the roster.
F. We can sign him and then trade him to another WCO team if their QB goes down in the pre-season. (Teams timid about signing him now would be singing a different tune after observing his good behavior here)