I recently upgraded to a P65+, and after thirty years also moved from Hasselblad V to the Phase One/Mamiya 645 system. Using the 645 prompted two questions, can I use this camera handheld, and what's the lightest tripod I can use with this camera?
I'm still deliberating but the answers seem to be that with sufficiently high shutter speeds (1/500s or more) I see little or no difference with 45mm or wider lenses between handheld and tripod mounted, and secondly a tripod that's too light (especially when used in windy conditions or without mirror lock-up) can actually be worse than handholding!
But to go back to your original Leica question, I recall that the noted Leica writer Brian Bowyer said back in the film era that most people dramatically overstate their abilities to handhold a camera, and for the very best results with M photography he recommended at least two stops above the normal guidelines, so 1/125s with a 35mm lens, or 1/250s with a 50mm lens. Yes, an acceptable shot of an unrepeatable moment is always to be preferred to no shot at all, but if conditions allow the speeds that Brian recommended then you can be reasonably confident of achieving results fully comparable with a tripod mounted camera.
