I am down to (when it comes to R bodies) a Leicaflex SL, and SL2, and two R8s. Have had a variety of SLs and SL2s, but never a plain Leicaflex, so someone else will have to cover that. The R8s have better meters, and higher available shutter speeds, (though the meters in the earlier cameras are more than “good enough), but they are all wonderful as daily users, as far as I am concerned. The Leicaflexes have a wonderful precision feel to them, and are a joy to use, IMO.
Yes, people have taken all the R lenses to use on mirrorless digital things, (though they are natural on Leica SL digital bodies) and they are no longer cheap, though the 50mm Summicron is still very inexpensive for what it is. Some internet research will tell you all you need to know. Leicaflexes are one of my all time favorite cameras. I actually use mine more than the R8 bodies, just for the feel of tripping the shutter. And the viewfinders, which are unsurpassed.
To people unduly obsessed with cameras being “light”, i.e. constructed from plastic and thin metal stampings, these are not for them.
Anyway, yes, no problems as daily users, for me at any rate.