Mizuno released heel and forefoot specs on its Wave Universe 3 and they are quite minimal as those of us that run in the MWU3 expected, but I was even surprised to see it's only a 2mm differential:
Heel (18mm), Forefoot (16mm); non-removable insole.
With the Nike Zoom Streak XC with only a 3mm differential and now the MWU3 with a 2mm differential, I'm going to seriously consider putting the MWU3 back into my core rotation in place of the Nike Katana and just run in the Nike XC, MWU3 and Evo.
At 3mm and less, I really can't notice any heel build-up. However, hopefully this puts pressure on other companies to zero drop because there will be plenty of shoes with very minimal heel differentials.