I'm on the fence on this whole issue. First of all, the scheme is effective if used properly. We know first hand, losing Super Bowl XXXII. I don't think there is an argument, that if played correctly, the zone blocking scheme works.
The problem lies in playing on the edge of the rulebook. I have several friends that are Bronco fans and I always point out their blocking scheme as borderline dirty. Now that we are going to use it, a small morale dilemma rises in me. I think the biggest problem I have with it is that a couple inches of miscalculation could result in a knee injury on the opposing defensive lineman.
I don't think the Packers have a league wide reputation as being dirty team, but this may jeopardize that.