I saw a really interesting article about how the Salary Cap actually hurts parity.
The whole premise was that it limits the way teams can build franchises; limiting the formula for success.
Essentially, teams may have an easier path to the playoffs now due to a bit of parity, but only the teams that are truly savvy at drafting well and managing the cap are consistently in the super bowl (NE, BAL, PIT, NYG, SF).
I don't know if I agree completely, but they used some good counterpoints. For instance, MLB sees more parity despite not having a cap.