I've just remembered one thing you should check for with the pre asph 35mm Summilux. There is a circular tube shield on the back of the lens. On some lenses the shield fouls the inside of the camera and doesn't quite allow you to focus to infinity on the M8. I'm not sure if the same applies to the M9. Not all Summiluxes have this problem. Mine did, but two or three others I tried at a dealers were OK. The shield can be easily removed by a competent repairer and the correct shape cut out to allow the camera to focus to infinity. If you think you may have this problem try to get the lens on sale or return.
Read through
this thread if you haven't already seen it. Also posts 5, 11, 43, 44 and 46 in
this thread which discuss the rear shield.
Bob.