Well, I figured it out - with no lights defined, I get an "all black" image but if I add an area light and crank up the range to 1000 I can finally see what's happening. Anything much less than that and it's completely dark.

I'm pretty sure that in the A6 days there was a default light that was bright enough to look around in a simple room; maybe I'm crazy or maybe this has changed in A7. In any case it seems to work fine with an added, bright light. Duh.

--BC