As you mentioned the AF cares about this since the lens is stopped down prior of focusing.
However, the same applies to manual focusing (on the A7R at least).
Thus the only way to experience an issue (if there is one) is to -say- focus manually at max. aperture and then stop down without checking. While this is viable it's still a bit of an odd workflow.
My typical speeds were below that.
In the real life, I used the 24-70mm (with activated OSS) mostly between 1/80sec and 1/250sec.
On tripod (without OSS) things start at 1/100sec (at f/4) - this seems to be a critical spot (also on the FE 35mm f/2.8).
I have the impression that the results are MUCH better at 1/500s and beyond.
Thus from a user perspective it may make sense to choose ISO 400 as minimum setting (I used ISO 200).
Boring Brick wall shots.
OK Part 1: seeing how different shutter speeds go on the A7r -- handheld Pt 2 will be tripod)
Method: boring brick wall, side light, five exposures taken with care OSS on @ 70mm on the FE2470 at each whole stop shutter speed from 1/30 to 1/4000
First finding: there's a lot of variation viewed at 100% at all speeds up to and including 1/1000 (1/1000 was best with least difference). And that's with OSS on!
I attribute this to camera shake; if you are shooting 36MP in a lightweight camera, you really need to pay attention to technique.I'll try again with my L plate or vertical grip or both to see if it helps.
Second finding: I chose the best exposure at each speed to be indicative of as good as you can get handheld, to see if there were differences. If so I'd attribute them to shutter shock.
Well the best 1/125 was just visibly worse than any other speed (including 1/30) at 100%. Not visible at 50%
I couldn't be sure if say the 1/250 was worse. Well within placebo range.
Conclusion: I'm sure shutter shock is real, but in the field handheld it's not I think the main problem. The main problem is that's a lot of pixels, and a very light camera, and you have to be very careful (and shoot multiple frames where possible).
The variation within a shutter speed was much, much, more significant and the variation between shutter speeds.
This variation lasts until 1/2000 at which point on there's not difference within a shutter speed.
It's quite possible that shutter shock is worse on a tripod (maybe holding dampens, and in any case the tripod will get rid of the camera shake variance and expose the ss.
But my take home message if you are handholding is unless you can use 1/2000 of a second there's no need to worry much about which shutter speed to use (except maybe 1/125 but even then it's not a biggie) but you do need to take a lot of care and shoot multiple images where possible and if the image is a good one.
So it's a challenge to handhold, but that's part of the fun....
Yes that's a reasonable thing to do (no-one NEEDS 36 MP, and what I most like about FF is the easier potential for bokeh and separation). Still it's fun...
But of course, assuming the OSS is as good an Pasasonics IS or Oly's IBIS, you aren't going to get *worse* results from the extra pixels: you'll just see it better when you go 1:1 (presumably when I couldn't see differences at 50% this was a similar magnification to 1:1 with m43). And sometimes you will get better results.
But whether it's worth storing the often useless extra data, and waiting longer for pics to load in Lightroom, is of course a personal judgement.
But there is more than resolution. With my GR resolution is not the problem but dynamic range. And I think with M43 it is still more problematic. Personaly I think the mechanical shutter will be the next part which will be removed. A ND filter instead would be very nice.
As an A7r user at least I have the option of the 36 MP FF sensor. Yes often according to the tests you won't be getting anything like full benefit of what the camera is capable of. Leaving aside considerations as to what my technique and capabilities are as a photographer, I will encounter conditions, hand hold, use lenses that won't produce the capabilities of the camera.
But the same goes for any other combination of camera and photographer out there. If you were standing next to me with your E-5 or whatever and I am achieving 12 MP on my 36 MP camera, what will you be getting on your 16 MP quarter frame sensor ?