the reason for the playoff was to fix the BCS because people wouldn't quit bitching about how it didn't get the best teams on the firld (though it did a surprisingly good job of getting the best teams relative to the amount of butthurt it caused). the reason for the BCS was to get one champion instead of having years of split national champions. I think the 4 team playoff accomplished that goal.
I understand the reason behind the BCS. And I understand the playoff was intended to fix the problems with the BCS. the question is whether a 4 team playoff was the best model for truly fixing the problem. It's a better model than what we've currently got, no question. But, if they were going to take the landmark step of abolishing the current system and enacting a whole new scheme, I think most fans would like to have seen it go a little further.
A big reason is because the big boys from different conferences rarely play eachother during the non-con and, as such, there is always some amount of subjective slant. An undefeated Pac12 team might not be as good as a 3 loss SEC team. A 1 loss big 10 team might be about the same as a 2-loss BigXII team. An undefeated cindarella (Boise, TCU) might be better than an undefeated ACC team. We don't know because there isn't any meaningful interleague play. Little guys like Boise, KU, Utah, TCU have routinely beat the bigger names in the past 6 BCS bowl seasons. When a Utah handles an Alabama or a Boise handles an OU in a BCS bowl, there will always be that question. That's why I think it would be better to grant AQ status to some select conference champs and then allow 2 or 3 cindarella season teams into the mix just to see "what if." I think it would be much more telling as to how these teams stack up. It would also solve the debate as to whether the little guys like TCU or Boise can actually do it on a week to week basis, as opposed to a flash in the pan performance after a month of preparation.