Has anyone wrung one out thoroughly?
Used one seriously over time with scored timed drills?

Never used my Micro Roni w/g32 (.357sig) in competition, but mine is 4 or 5 years old and still has a good solid lockup in the brace hinge and the pistol capture mechanism.
Never had an issue with shifting zero although I’ve swapped from a reflex to a short scope and back to a different reflex sight.
Compared to all my other braced pistols it’s noticeably lighter, shorter, and has less recoil.
Mine has the original short brace, not the longer optional brace that came out later. Feels similar to an M4 stock fully collapsed.

What's your practical effective range to hit a paper plate?
Would you buy it again?

If you keep in mind its a chassis to make a pistol a little bit better I guess its not awful

I had one for awhile and simply wasnt impressed. I did have zero issues. Then again mine did have a plastic top rail.

However I come from using dedicated PCC platforms so

Is it paper plate accurate at 25 yards? Sure. But thats not something I would brag about.

I can’t say how accurate other calibers perform but at 50 yards I’m consistently making 2” groups with my g32 in a Roni.