The Sony A7R IV seems improved in every way in terms of the camera itself: better button feel, best EVF for manual focus in ANY camera I’ve yet used—awesome! Operational speed is improved but still a bit sluggish to do things like zoom into a recorded image, though scrolling is very fast.
One thing I’ve learned is that even some very good lenses are going to struggle with the sensor resolution of the Sony A7R IV! Color fringing shows up in unexpected places, like the Voigtlander 110mm f/2.5 APO-Lanthar.
You will not get full resolution without focus stacking because depth of field relative to pixel size is substantially reduced. Which is awful in practice, because there is no automated focus stacking support on the A7R IV. The huge file sizes are ridiculous too—often larger than the lossless-compressed files with the 100MP Fujifilm GFX100, so much so that I anticipate running out of card space in the field with the A7R IV.
Sony 4-shot pixel shift remain a science fair project outside, even for static subjects—checkerboarding is almost impossible to avoid, at least on all-critical edges. its 16-shot pixel shift mode is just lot of soft pixels often inferior to 4-shot mode—and both suck compared to Panasonic S1R Multi-Shot High-Res mode.