Shooting at high ISO is something we now expect from modern cameras.
Last night I decided to test the Leica at ISO 10,000. This is ridiculously high but was a fun test. So after the sun was set I headed out and walked around the local village to grab a few test shots.
These were all shot at f/1.4 or f/2 and at 1/25 second for the top shot and 1/125 of a second for the church shot.
There was colour noise and grain, which I enhanced slightly by adding artificial grain, but the colour noise was easily dealt in Adobe Lightroom.
Considering this is ISO 10,000 its way better then ISO 640 on my Leica M8.
The shot below was the M8 at ISO 640 at 1/30 second. Its good but not in the same class as the M10.