It's been over a year and I still use my standing desk. Every (working) day.
I don't keep specific metrics, but I would say I stand about 80% of the time and sit the remaining 25% of the time (you see, I work 105% long days).
Some days my feet are sore at the end of the day, but a good walk will erase these pains.
I think my mouse is at the wrong level -- for the first time in my life my mousing wrist is occasionally sore, to the point where I can't put a load on it. I suppose this is "RTS" or "corporal's tunnel" but it's nothing some good heavy lifting hasn't fixed.
As for my health, I have no idea if this has worked for me. My legs are indeed stronger than they were before, and it's effortless to have to stand all day in other scenarios outside of work. i.e. I no longer need to find a place to sit down because my legs are sore or tired. This is good for outoor activities where sitting isn't an (immediate) option.
I wonder what will happen in a decade to my feet and knees.