A friend of mine works for Ricoh, though not in the camera arena. I think he has a GXR. It might be worth seeing if someone will have a Leica module after it's released so I can play with it. So I'll wait and see.
That said, the modular system is kind of both genius and retarded at the same time: there definitely are advantages to sealing the unit (dust and all that), but it does make certain repairs more costly. I hope the sensor's worth that kind of commitment, though I remain doubtful. Also, it seems like the modules would be a PITA to store as square/rectangle shapes don't pack as closely as smaller round shapes.
My first thought, though: I'd rather use Leica lenses with a rangefinder -- any rangefinder -- 99% of the time.