Got my RRR one-arm jack and really like it. A pure slicer of course, but wonderful at that particular job. Thin high grind, came shaving sharp (not a perfect grind by any means but way better than Case), fit and finish generally at least on par with Case (only issue is very minor gaps in a couple of areas, can see a bit of light when backlit but otherwise not apparent.
Gave it a flush and some Super Lube and the walk and talk are satisfying, I'd say again on par with my small set of experiences with Case. Perfectly flush springs open and close, a tiny bit proud at the half stop.
The one-hand opening gives me absolutely no trouble, I find hooking it on a belt loop feels secure and comfortable. Take 1/2" of length off the pattern and add a secondary wharncliffe or coping blade for when you need a point and it'd be perfect.
Will not hesitate to snag some more in the future.
Edit: On second inspection side by side with my Peanut, I take it back: RRR has significantly nicer fit and finish.