On the pre-production models, with K and M lenses, you get metered wide-open operation in AV mode, only. The aperture simply will not stop down to the value selected on the aperture ring, but it will stay wide open all the time, when DOF previewing as well as during exposure. The metering and automatically selected shutter are correct for wide open.
With Ks and Ms you get nothing. No metering at all so you will have to use a hand-held meter or guess. some have suggested adjusting to ISO settings to use these lenses but I have no idea what they mean.
To override this behaviour, one can unlock the lens and turn it 15 degrees anti-clockwise. The aperture levers of camera and lens disengage so that the diaphragm stops down. In AV mode, one can thus have real aperture metering. However, one must take care not to drop the lens. To avoid the danger of dropping the lens, "you would have to make a simple modification on the lens mount, making a second notch 9 mm from the first one (to lock the lens at the right position)", just like Andre wrote.
In manual mode, a K or M lens would stop down, however, no metering is available.
However, there may still be a tiny little hope that the production model (or a later model) behaves better.
Arnold
