...if I'd written or directed it, those drone heads would have landed on people, encased their heads, and converted them from the neck down...
I will admit something of a missed opportunity. I was fully expecting that.
Since that was not the direction they went, a flying variation upon the cybermats would have made more sense.
I can guess the rebuttal, "But, Bill, that would have meant designing and modeling a new cybermat concept. They already had Cyberman models for the 'floating in space' sequences." True, but those helmets were modified to have glowing "thrusters" (anti-grav emitters, whatever). Since mods were required anyway, it seems to me they might have been able to tweak the "Bitey" mesh (assuming one was coded for certain shots in the Matt Smith episode).
Of course, what was depicted did not frustrate or anger me enough to pelt the TV with spoiled jelly babies (can those things actually "spoil"?), so ultimately, it's not that big a deal. I would like to learn what was the "behind the scenes" reason for going with the flying heads, though. Simply for a hoped for "creepiness factor"?