My grandfather was an avid Leica photographer from the late 50s until he passed away in 1995, and my dad inherited his gear.

More recently, my dad also has one of the Leica D-Lux models (basically a rebadged Lumix - they both use Leica optics and Panasonic electronics). It was good, but I'm not sure it was really worth the price premium over its Lumix counterpart.

I'm not familiar with their current rangefinders (which as you know are their flagship products), but as I understand it, the rangefinder was a more accurate way to manually focus back in the days when that mattered, and the form factor of the current M-series is largely rooted in tradition. They're still known for quality optics though - it's personal preference whether that's worth it the price premium.