I'd like to compare viewfinders, multi-shot file quality, shutter vibration and a few other features before drawing any conclusions. My a7II's viewfinder, while much preferable to the D800 (IMHO), leaves a lot to be desired and the loss of bit depth when using multi-shot mode and lossy compression compromise the file quality. The a7II's EFC feature makes the camera more responsive and quieter but with adapted lenses it's useless at shutter speeds faster than 1/1000 sec. There's a lot of room for improvement in the a7-series.
Shutter vibration with the A7rII is minimal. Lossy compression has been eliminated with the latest firmware update - there's now an option for uncompressed RAW. What's wrong with the viewfinder? It's not an action viewfinder (weak battery = slow processor = increased viewfinder lag) but, for anything other than action, it's more than good enough. And, if you're shooting fast action, you're probably going to be using an SLR anyway.
On the other hand, you're losing a lot of resolution (24MP vs 42MP), and, going on past record, likely a bit of DR as well. So, essentially, you're trading a few 'soft' features (which may or may not matter, depending on shooting style) for the loss of some 'hard' image quality (resolution), which affects each and every file - even if you only need 24MP, a 24MP file derived from downsampling a 42MP file is almost always better than a native 24MP file.
I can't see too many people finding that a worthwhile tradeoff, particularly at three times the price.
Still, I'm very interested in seeing what Sony brings out with its upcoming 'professional' E-mount camera - let's hope it's based around the A7r sensor or its successor (or comes in a R and S version, like the A7) and has all the missing features such as dual cards, faster AF, less viewfinder lag, etc.
