Your right, Milorginate doesn't add beneficial microbes to the soil. What it does do is to provide very active exchange sites for microbial populations to increase.
The USGA Agronomy section has been studying the effects of micrbial populations in sterilized soils (particularly greens mix for putting greens construction) and has reached an interesting conclusion. Sterilized sils will repopulate them selves to pre sterilization levels without any need to add microbes. Kind of shoots a hole in the organics/microbe adding theory.
Another thing, processed fertilizers that are naturally urea based (milorginate, sustaine, turkey/chicken litter) do not, as previously posted, contribute micorhizal or other bacterial to soils. The benefit of some alternate N sourced fertilizers are the micronutirient sources.
This is what provides some benefit to organics and trace package use.
Dan has a good point, a good balance will incorporate synthetic and micronutirent containing organics/trace packages.
One other point, the alleged microbe supplying organic fertilizers, what is the shelf life of this material?
Interesting discussion so far.