I know I'm probably in a minority on this, but I wouldn't allow convicted felons to play in the League. Re-instating Burress and Vick has sent the wrong message to kids and also to other players, who see a lax approach by the League office to criminal activity and then, for example, use an NFL team as the basis for a major drug operation (Chicago)
I appreciate that people make mistakes and, in my own life, I am a very forgiving person. I would bend over backwards to accommodate people who've made mistakes and are genuinely seeking to turn their lives around; I just think the line should be drawn at a felony conviction.
If someone is rehabilitated after serving his time, then let him find other ways to make a living and/or serve the community.