Well, I pulled the trigger: last night I bought a 2019 Salsa Mukluk. I intend mainly to use it as a winter commuter, but I couldn't resist the urge to ride it to work today.
Being an end-of-year clearance bike, the shop had knocked $700 off the price. I then used my credit card rewards that I had been saving for the last 4 years to cover the balance. So basically, free bike! I paid the shop to convert the wheels to tubeless, and then bought a rack from them and had them install it. I had an extra bike computer and platform pedals sitting at home, so I installed those last night.
It was slow, but no slower than I had expected it to be. It probably is about the same speed as my studded winter tire bike when riding on pavement: 10-11 mph average. I had a brisk head wind this morning so that didn't help either.
I still have to work on dialing in the fit. I also have to figure out some sort of fender system.
I definitely didn't need to call out to let pedestrians on the MUP know I was passing; those big knobby tires are loud enough that they could hear me coming 50 yards away.