i have both a 5dmk3 and a sony a7r.. here are my thoughts on it..
if you bought the sony a7r and a metabones adapter expecting the same performance as a native lens you will be disappointed.. especially dealing with autofocus.. also.. if you expect to take amazing shots with the camera an hour or two into having it.. you're probably going to be disappointed too.. its a tool.. and it definitely has its pros and cons.. but give it a a few days.. and dont try to use it like a canon camera.. its NOT a canon camera.. take some time to learn how it works.. and the menu system. i bought it right when it came out and i'm still getting used to it.
my thoughts on the Sony a7r:
-its def a first gen product.. but a VERY VERY good 1st gen camera. with the sony 55mm f1.8 and 35mm f2.0 auto focus is fast, and photos are incredibly sharp.. is it as fast to focus as my 5dmk3? nope.. but fast enough for street portraits and day to day shooting, yes very much so. i even bring it into concerts.. works well.
-with the metabones adapter it takes 2-3 secs to focus with a canon lens. (most of my experiance is with the canon 16-35mm f2.8 L ) it hunts ALOT.. and you might have to hit the focus button/shutter button a few times for it to focus correctly.. but when it does lock on.. its good and sharp... but it does take a little finess and some patience. the metabones adapter and canon lenses wouldnt be suitable for much more than landscapes and very patient models if you plan to rely on the autofocus.
- focus peaking works very very well. honestly i have pretty much given up on the autofocus with the metabones adapter.. but metabones + focus peaking works very very well.. it takes some practice but once you get it... it works really well. i've been using it with the 85mm and the 135mm f2.0 and had very good results.
- i did a lot of testing right when i got it comparing it to the 5dmk3.. everyone has different tastes.. i'm a slow shooter.. i dont shoot any sports.. but the sony images were (and are) much sharper than the 5dmk3.. i think it has a lot to do with the lack of anti-alising filter.. but it is noticeable.
- battery life is TERRIBLE.. not just bad.. but TERRIBLE.. you get about 300 shots per battery.. so an all day trip takes 3 or 4 batteries for me.. luckily they are pretty cheap.. and charge in about 3 hours.
- luckily you can reprogram pretty much all the dials and buttons on the camera.. i wasnt happy with the default setup at all.
- i too thought i had bricked my camera with the firmware update, luckily the forums had much better instructions than what came from sony and eventually got it to work.
- lens selection is really limited.. canon lenses work with the adapter but its NOT the same as native sony lenses.. the 55mm f1.8 lens is amazing.. the 24-70m f4 is very nice.. but not as sharp as the 55mm prime.
- bracketing/HDR is definately rough around the edges with this camera.. it has some settings but they arent as nice as they should be. you cant set the bracketing and use the timer.. hopefully this will be fixed in a firmware update.
as for the 5d mk3.. i still have it and i dont plan on selling it any time soon. i have a much better lens selection, and it definately does focus faster.
i seem to pick up the sony more.. and take it out more.. its fun to shoot.. its a little more work.. it takes more time.. you have to think abotu your shots a little more.. and be patient.. you also cant just hold down the button and get 1 good shot out of 20 all day long. but at least for me.. when i do get a good shot out of it.. it really does blow me away. 36mp, no AA filter.. gives you LOTS of pixels to play with in photoshop.
Thanks. I am renting a A7R this weekend and glad I did not buy it. It is very rough around the edges, I am having no luck with AF and the meta bones IV adapter with 180 macro.
Hoping that Canon does something this Sept to dramatically increase DR so I don't have to buy a A7R. I could live with it but would rather not.