Upload & Sell: Off
which the 35/2.8s are you thinking of? none come immediately to mind other than the summaroon. i agree that the rendering is super exciting though.
The Contax, the Nikkor AI-S (has a bad rep, but I own one, and it is great, even on my D800), and there is another which slips my mind. Maybe also the ZM 35/2.8. None of them are quite as good as the Sony-Zeiss, but these are *ancient* and/or much cheaper lenses, and perfectly good for use with current cameras.
If you want AF or EXIF, if you like native lenses, then there are good reasons to buy this, but at 800 Euro (!!!) this isn't a no-brainer, by a long shot. This is barely less than the Sigma 35/1.4. At that price I would probably just get the ZF 35/2.
I swing back and forth on the usefulness of the A7/A7R as the basis of a kit, as opposed to an alt platform. I could imagine getting the RX1 and the A7 with a Summarit 75mm or something similar, but Sony has done that thing again where there are a couple of semi-interesting native lenses, a couple of slow zooms, everything with its own non-trivial compromises (speed and/or quality). It will be interesting to see how long it will take them to do what Fuji is doing, i.e. a nice, sharp 21/35/50/85 kit.