I haven't read all of this, but I've read a chunk of it.

I'm in the camp of it can't matter unless the frame is deflecting enough to cause the chainring and cogs to be significantly misaligned creating friction (heat). The magazine articles that claim X set of cranks is 'noticeably stiffer' than Y set of cranks seems silly. What is the magnitude of crank arm deflections?

As far as the frame itself goes, it seems to me that the 'buzzing' we feel in some frames and 'damped' feeling in others is really our best way of measuring stiffness. If a frame is 'buzzy' and transmits a lot of high frequency vibrations through the frame and to your butt and hands, then, by definition, it has a (relatively) high natural frequency and the transmissibility of high frequency road content is greater. Likewise, a frame that we would consider 'flexible' would have a low natural frequency and the transmissibility of high frequency road inputs would be relatively low.

I'm not really sure what kind of frequencies we're talking about, but to throw some numbers at it, let's say we're traveling 30 feet per second (20.5mph). If the rocks in the pavement have an average size of 1 inch, then the input frequency of pavement aggregate would be 360 Hz, or, musically speaking, 4 notes above 'middle C'. That could very well be felt as a 'buzzing' through the handlebars.

So could it be that the 'damped' feeling from carbon and titanium frames isn't some magical material attribute, but it's just simple a function of frame stiffness? It think that it's very likely so.