I finally received my Studio Display after 3 months delay.
It's connected to my Mac Studio (as well as an LG Ultragear 27GN950 for gaming).
I've been using it for about 2 weeks now.
Impression overall: well built, great picture quality, good sound quality. I was coming from a 27" retina iMac so it's all very familiar.
However one thing that's really noticeable is the slow response time of the display. It feels like there's a slight delay in about everything, whether it's typing, clicking on menus, using the mouse (trailing), etc. It's almost like you're working on a remote desktop over internet.
Perhaps I've gotten used to (and spoiled with) the LG 27GN950 which is 4K 144 Hz, and only 1 ms, but I can't recall this laggyness on my iMac 5K. I couldn't find similar reports from others, so I guess I'm just having to get used to it (or maybe a future firmware update?)
EDIT: another thing I noticed is the sound level ramps up real quick. With only 3 blocks (out of 16) in the sound slider (fn+f11-f12) it's already very loud. This could have been tuned somewhat more proportionally imo.