One of the biggest challenge when shooting at wide apertures, is that the timing between distance to subject and his expression must be perfect. This is even more true with a rangefinder as you basically have very little time to reajust focus in these kinds of moving situations. Most of the time, you get only one of the two right (focus or expression), and every once in a while both. The best way around this problem : F8 and be there.
Not my way to shoot though.
Leica M9 with 35mm Lux Asph at F2.8, 1/750, ISO160