Users want gadgets that they can wrap their head around, they won't care about "Uniformity Across All Devices and Carriers" also carriers and device makers will certainly not appreciate this move.
Apps matter the most, but I think Microsoft will be stuck in catch 21 on this one, the fact that they want tighter control over the phone only makes things horribly worse: for apps, you need critical mass, for critical mass you need devices, but that will only happen if carriers and device makers embrace WP7, but they will probably ignore it, because they can't differentiate themselves because MS wants control.
So unless Microsoft makes something that is leagues better than the iPhone, they have zero chance to compete. Why the iPhone and not Android? Because both of MS and Apple want to have full control, which most device makers reject.