I like it. Easier to access control center with a button press regardless of where in the watch you are (swipe from the bottom only worked for me on the watchface, never in apps).
Stacks are nice and they let me use less “complicated” watchfaces without the feel of missing out on functionality. Though I’d love to be able to set up different stacks per watchface.
The idea is not really to make you stand (it’s scientifically proven that both sitting all day and standing all day is bad in a different way), the idea is to get you moving, because what is clearly bad for you is keeping the same posture for a prolonged amount of time. Other devices call the same feature “Move alert” and not a “stand alert”