I didn't swap, but i just get Sony without swap or sacrificing Canon.
I just bought A7R, and it is an amazing camera, i now many will moan about AF speed or high ISO capability, but i use this camera not in those areas, if i shoot fashion or still life or landscapes then i don't need much that AF rocket speed and i don't shoot at high ISO too, those scenes mostly need low ISO and not fast actions as well.
I would like to test and see A7RII by myself, i saw some RAW and it is unbelievable camera, but i keep reading about issues here and there, but really i don't know if i must find issues with any new camera, i don't use any camera for 100% all types of photography, i feel and understand that many want one camera for everything and it has all whistles and don't look for upgrade for years and years, as you were using 5D2 for a while, 5D3 is better by miles, and A7R quality at low light surpass that 5D mk3 quality, i have 1Ds mkIII and 1DX and i still choose my A7R always for static or still photography non motion/action.