Look what was waiting on the front step when I got home - my Instant Pot Max!
They're in stock at Amazon with immediate shipping. (Much to my surprise. I didn't know it was coming until I opened the box; I missed Amazon's "we're shipping" email on Sunday.)
From my couple of minutes with the Max: It doesn't have the twitchy knob that the Ultra (hooray!). It feels substantial, with heavier weight and higher build quality. And...that's all I've got in the few minutes I've played with it.
More to come once I've had time to put it through its paces, but for now...my new toy is here. Whee!