I'll go one farther on the electronic shutter: I hope Sigma releases some i-series lenses with built-in leaf shutters. There's some precedent for this, and with cooperative firmware, could be used on other camera models as well. (It would be even more beneficial for cameras with flash control.) I'd gladly take a lens that's a stop darker and a bit more expensive in exchange.
I’ve pretty much settled on Sigma lenses on my BF but will likely try my M lenses more seriously at some point
My 45/2.8 is pretty much always attached. The only time I go back to m-mount is for my little 40/1.4 Nokton Classic when I know I'll be in the dark. And once I used my SLR adapter to fit a macro lens to it. I didn't expect to like the 45 as much as I do, but I did expect my adapted lenses to quickly be set aside once I had AF lenses for it. I spent years working in a camera store, listening to people say "well, if I buy this new camera system at least I can use my existing lenses on adapters", which was their way of saying "I'll see you again in a few months as I start re-buying all of my favourite lenses".
I have read the reviews and looked at the Sigma BF technical info, and seen bunches of photos ... And I just don't get it at all.
The good news is that you're not missing out. Nobody with a BF knows something you don't, or has any capabilities that can't be found elsewhere. The BF has a good but common sensor, it's about the same size as other small cameras, its autofocus isn't the best in the world, and it's suitable but not particularly gifted for adapted lenses. It's not a cheaper Leica, but it's also not a more expensive Panasonic. It's just it. And that's why I love mine.
The Sigma BF is an object. All of my other cameras are devices.
A cut crystal vase, or a golf club, is an object. I've never played golf, but if I pick up a good club, I know it's a good club and can see how it's meant to be used. There's a solidity, a thing-ness, to it. My ice maker, or my TV remote control, is a device. I've owned some good TV remotes, and I've had ones where it isn't clear which end is which – but regardless of design success or failures, their purpose is what they do, not how they're used. There's more to this distinction between the BF and other cameras than that in my mind, but maybe in my mind is also the only place where this makes sense.