Ming Thein has a brief but informative piece just up with results of testing different M-mount lenses on the X1D with the electronic shutter function:
https://blog.mingthein.com/2018/03/17/leica-m-mount-lenses-on-the-x1d/
https://blog.mingthein.com/2018/03/17/leica-m-mount-lenses-on-the-x1d/