Imo, you're requirements are very different from the average Mach3/LinuxCNC/UCCNC user. 95% or more of the user base has no need for the specs you're spouting.
Neither Mach3, nor UCCNC, is a replacement for a true industrial control. And they don't claim to be.

I don't really care how many ms feedhold takes. UCCNC stops as soon as you it the button. Whether it's 1ms, or 100ms, you still have to reach for the button, and wait for the machine to decelerate, both of which take a lot longer than your 1ms response.

UCCNC has itīs own set of issues, which I cannot properly debate since I do no use it, but are quite well documented by many users.
You could at least mention what you're talking about. Bugs reported to CNC Drive are typically fixed in a few days, usually as fast as 1-2 days.
There are no "issues" that I'm aware of, unless you're talking about missing features.

I don't use a lathe, so I don't care about any of those features.

The machine homes to the nearest step, whether it's at 100Khz or 4Mhz, the machine still homes to the nearest step.


Who else has 1 ms feedhold ?
4 Mhz threading ?
Glass scale feedback at 4 Mhz ?
4 Mhz homing ?
Hw MPGs with instant feedback, due to 1 ms update loop ?
High-speed servo spindles, with differential signalling, for rigid tapping on mill and lathe ?
24V industrial IO ?
All of these are CS Labs features, not Mach3 features. Mach3 is an open loop control, so glass scale feedback is not even used by Mach3.

With UCCNC and the MB2 breakout board I'm using, I have instant feedhold. Instant FRO and SO using analog inputs. Instant MPG feedback. Rigid tapping. Differential step/direction, and 24V I/O. For about 1/3 the price of Mach3 and a CS Labs controller.

And with it's superior trajectory planner, I've seen UCCNC run 30% faster, while making more accurate parts than Mach3. At the end of the day, that's what matters to me. Not if the feedhold response is 1ms.