Werner:The 24-70 is in everyday use much better than its reputation or as some internet tests would suggest.
On the positive side is its versatility and convenience and one should not underestimate these two. The zoom range ist very useful, AF and OSS are working with no problems. The lens is in 90% of its range very sharp almost around the whole frame. Micro contrast is very good.
But it is a zoom lens and that means some sort of compromise. It can not be as good as premium primes.
The corners at 24mm never get perfect even stopped down. But do you really ALWAYS need perfect sharpness in the very corners? My answer is: NO, you may sometimes need sharp corners, architecture or some landscape shots come to mind. And only when you want to print these very big.
On the long end 70mm it is better to stop down a little.
Besides the extremes 24 and 70 the lens is very good with a peak around 40-50mm.
The weakest part of the glass is it's distortion which is very strong over the whole range. A compromise to build the lens relatively small and light. The distortion gets easily corrected in cam with Jpegs or with the LR profile. The same applies to some CA's that can occur.
With the A7R and 36mp i see no problem or image degradation with these software corrections. Even with my excellent Distagon 21/2.8 i have to correct distortion when straight lines are important for the composition.
I can not speak for the 7 or the 7s. I think it will be no problem with these either as almost all MFT lenses are build with software correction in mind.
Bokeh is of course not the strong part of the lens.
So, when would i use it? Every time when i can take only one (or two) lens to the location, size and weight are matters.
When not? For very critical work and when i can take 3 or 4 primes to the shooting and have time to change lenses. When i am looking for optimal bokeh, i would oc. not use the 24/70.
I hope my few words could help.
Your words were precisely what I wanted to know. Thank you for the time you took composing them.