Cool article! I've owned one of those lenses, the Canon 50/0.95 (on a Canon 7). Not an easy lens to focus wide open, but it can see in the dark. A couple low light (~1/20s, f/0.95, XP2 rated at ISO 800) samples:
I have the 50/0.95 for the Canon 7, and it is amazing for a 50 year old lens.
But with the price they go for, and the cost to convert to a Leica M3: Buy the Cosina/Voigtlander 50/1.1 Nokton instead. It is sharper wide-open, uses 58mm filters rather than 72mm filters, obstructs much less of the viewfinder. These days, the Canon with the cost of conversion runs $2000 and more. I paid $200 for mine when things were sane a few years ago. The Nokton at ~$1000 is a bargain.
If you've read Ken Rockwell's review of the 50/1.1 Nokton on the M9: Ha. The Nokton comes out of the box optimized for film. Should be fine on an M3. For digital- I built up the cam by 0.05mm for the M8. Focus is spot-on.