good idea. i forgot to mention the use of a magnifier with the noctilux and summilux, particularly useful for people who wear glasses. here's the one i use (search for megaperls on the forum):
MS-MAG x1.35 magnifier for Leica M
[MS-MAG 1.35] ¥16,900 
Magnifier for Leica M viewfinder. Multicoated. Includes dioptre adjustment facility (-3.0 - +1.5).
greetings from hamburg
rick