What we've established here is "it depends." If someone wants to shoot with zooms, then there is little to be gained in lens size and maybe weight. But if someone makes it a priority to find very high quality prime glass, then there are ways to save weight and especially size when choosing the a7r. I agree with Barry it is no panacea. But these cameras offer options that DSLR's don't (and vice versa of course).
I was a Canon shooter since the early 90's. Although I switched to medium format in 2011, I still needed a more versatile system, and my 5d was getting old. Canon didn't have anything exciting to me, and I didn't want to switch all my lenses in order to get a D800. When the a7r came out I thought it was perfect because I could use all my Canon glass. But after I got to know the camera, I realized I was wasting a great potential for a smaller system. I had a Zeiss 21, 24, 35, 50 and canon 90 ts. I replaced that with the two Leicas (WATE and 90) and two Sony's (35 & 55).
Equal quality (using my constraints), smaller and lighter kit.
Dave