Thanks for sharing your experiences so far with the new Sony. I should probably not comment as I guess you could call me a Leica "Fanboy"!
I think its a testament to Leica's long standing position in the photography field when many try to figure a way to get Leica's lenses to work on anything other than a Leica body. Of course it wasn't Sony's intention for this to happen with their latest body, the A7(R). But as a full fledged replacement to shooting with a Leica M and Leica lenses I don't think so.
But if one only shoots with say the 50mm or longer then this may give one a chance to experience a partial Leica experience as I've seen most lenses wider than the 50 have one issue or another on especially the A7R. As an aside my move to Leica came about after shooting a year with the Ricoh GXR-M with Leica Summicron 35mm. The Ricoh was a nice camera but with its cropped sensor there weren't too many options finding a suitable fast wider lenses.
Having said that, Sony has gotten a lot of attention creating such a small body with an excellent sensor. We will just have to see how their lens roadmap develops as in my opinion this is still an experimental system just as Canon and Nikon SLRs were in their early days. It's takes more than a couple prime lenses and a zooms to make a complete system.
I think its amazing what Leica has been able to do with their existing lens inventory and adapting them to today's technology. I'm not saying they're perfect or the best in every way. But as a mature "system" and one that is very compact in relation to the other full frame cameras Leica's product is hard to beat.
CV12, CV15, ZM18, 21 Lux, ZM21/2.8, 21 SEM, ZM25, 28 Cron, CV35/1.2 II, ZM35, Canon 35/2 LTM, RX1's 35/2 Sonnar, ZM35C, FE35, CV40, 50 Lux ASPH, Canon 50/1.4 LTM, CV50/1.5 LTM, ZM50C, ZM50P, FE55, CV75/1.8, ZM85/4, 90 Summarit.
Most lenses performed better or more 'naturally' on the M9. The widest decent non-native lens were the CV12 and 15 with very similar edge performance on both cameras, though both also have very strong vignetting and color shift. The CV35/1.2 II was the widest and least problematic. The 21 Lux also wasn't too bad, but lags in the outer zone until around f/5.6. The FE55 bests the other 50s for across frame consistency, though the Lux showed higher central performance while the ZM50P was decent, but seemingly a bit lower on the resolution scale. Everything longer than 50 was pretty much a draw, as would be expected...