Tjspiel: fwiw, I don't think you and I really disagree all that much! I don't think there IS a universal 'ultimate commuting platform;' there probably is one for each rider given his/her preferences, age, fitness, and prevailing commute conditions -- the basic 'type' of bike defining that platform will depend on those conditions. For me, it's atb; for you, road. What I was/am reacting to (as light-heartedly as possible) is simply the tendency we all of us have to universalize our own preferences.
Commuters can ride atb's (or a road bike) for all kinds of reasons, some related to economic necessity, some to convenience, and -- yes -- some to experience/experimentation/conscious decision that that kind of bike works best for the given rider in a given set of conditons.
Having said that, I stand by my further general point that for most non-pro riders, the 'speed' difference, on pavement, between drop-bar road and flat-bar atb (assuming road tires) is not as great as is sometimes stated.