My intent is to use my Leica R and Nikkor lenses with the Sony A7, treating it as a "Leicaflex SL Digital" surrogate essentially. I specifically went for the A7 rather than A7r not only because it saved me a thousand dollars but because I believe the A7's 24Mpixel sensor is more likely to be kinder with adapted lenses than the A7r's 36Mpixel sensor due to the differences in photosite pitch and AA filter.
I ordered Nikon F -> NEX and Leica R -> NEX adapters the same time I ordered the A7. In preliminary testing, all my lenses (R 50 to 180, Nikkor 50 to 105) work beautifully on the A7. No corner degradation, no color shifting, etc. Given the focal lengths, they probably work fine on the A7r as well. I have an Elmarit-R 24mm f/2.8 arriving soon—I'm hoping it works as well as the 50mm lenses do.
I heard the M-Rokkor 90/4, M-Rokkor 40/2, Nocton 40/1.4, and Ultron 28/2 work well also. This piques my interest since I own those lenses and they're a lot more compact than the SLR lenses, good for a compact traveling kit. On that basis, I ordered an M-mount -> NEX adapter as well. Waiting for it to arrive so I can test..
The short CV Color Skopars (21/4, 25/4, 28/3.5, 35/2.5) have always been somewhat difficult on full frame sensor cameras due to the lens design - near-symmetric, small lenses that put the primary nodal point close to the sensor. However this example that my Paul made with the 21/4 made with the A7r convinces me that I should try them on the A7 as well:
http://www.getdpi.com/forum/564309-post2381.html (link to Paul's post)
For situations where ultimate corner resolution isn't all that important, I don't see any reason why I shouldn't use them. I'll be curious to see how they work on the A7 vs on Paul's A7r.
That's a good thread to browse through looking for what can be done with which lens and camera combinations, btw ...
http://www.getdpi.com/forum/sony/49391-fun-a7-7r-48.html (link to the fun with thread)
I'd say you can't go wrong with the A7, buy the A7r if you want to push the envelope a bit further. ;-)