OK,
So I went to adorama today to try out a Sony a7. The build isn't that bad and the focusing, menus, and EVF work fine.
The camera's build and ergonomics are probably worse than the D700 but "good enough". I'm most unsure about the manual focusing in picture taking situations. I would prefer to use AF with this camera but I'd rather continue investing in LTM/M lenses too, so I'm probably going to use the camera in MF-only with M lenses. MF worked fine at the store but I need to own the camera and use it for a while to get a real feel for it. Maybe I'll get that 55/1.8...
I'm leaning towards the a7 over the Nikon because of it's form factor. I think the D700 offers a better shooting experience given it's ergonomics and OVF, but the a7 is easier to carry. Honestly, I spend much more time carrying my cameras than shooting them.