I just upgraded from the Sony A7rIII to the A7rIV. In the last years I had every „A7r“ camera Sony made. I startet with the A7r in 2015, when I switched from Canon. In the beginning I used my Canon lenses with a Metabones adapter. Later I changed lenses to Sony and get rid of the adapter. In 2016 I upgraded to the A7rII. This was a much better quality and Sony improved the camera significantly. Only downside were the batteries. For a serious use I needed 5 batteries ! This was the reason for upgrading to the A7rIII in 2017. So far I was very satisfied with this camera. But also good things can improved. So when the A7rIV was announced I immediately ordered one. My first impressions are positive. I like the deeper grip, the locking for the exposure compensation dial, the higher resolution and the updated viewfinder.
I have experienced the whole development in the mirrorless market. So far I am glad I switch to mirrorless early. But there are many improvements I still miss: the GPS synchronization and the phone connectivity is not reliable. The Sony app is not up-to-date. I do not understand why Sony discontinued the apps inside the camera. They had a big potential.
So far I am very pleased with my currently setup. When I travel I use the Fujifilm GFX 50R with the 32-64mm f4 and the Sony A7rIV with the Sony 100-400 GM. The cameras are always attached to the lenses and I don’t need to switch lenses at all. So I can easily avoid sensor dust which is still a big problem for most mirrorless cameras. If I hadn’t the GFX already, I would have kept the A7rIII as a second camera.