i too have been using an a7r with a metabones adapter and canon lenses.
So far i've been very impressed. Focusing is slow but not as slow as i expected. it takes about 1 sec to 2 sec to get a focus lock.. not good enough for action shots but perfectly fine for portraits or landscapes. i havent had much time to take really good shots.. but here is one with the 16-35mm L lens. http://www.flickr.com/photos/darrellrhodesmiller/11693761616/#
as for camera handling.. it "feels" very different from my 5dmkIII.. battery life is pretty terrible.. you get about 300 shots per battery.. its small and light.. buttons and dials are nice.. but very different from canons interface.. HDR is a pain, without the option to take 3 consecutive bracketed shots quickly, you have to press the shutter each time. filesize for raw is surprisingly small for being 36mp.
VERY loud shutter, but i kind of like it..