Thank you for sharing your experience. I’m still using a 500 stick and have had some frustrations, but I recently bought a 2 m USB extension cable so I could move the stick to a more elevated, “open to air” location - and that has made wonders for my network (although it has fewer devices, it covers both the house and the stable/barn so it has some “signal strength challenges”). For those that haven’t tried it, I can warmly recommend trying putting the stick on a cable so you can place it freely.
Regarding the slowness of reactions, I think there are multiple factors, but I’m convinced that one of them is in OH core itself, and not really related to the Z-Wave binding. I have done some modifications to threading in Core that basically seem to eliminate this whole “OH slowness” and seem to make things react much more “instantly”. This obviously doesn’t mitigate any slowness in the Z-Wave network, but the “Core slowness” comes on top of the “Z-Wave slowness” and it’s not always apparent what is what.
I made this marketplace add-on recently to address this issue. It seems difficult to get people to “get” what it does, but very simply: Once installed, you can put XML files in $OPENHAB_CONF/thingtypes and have OH pick them up instantly. The files use the same XML file format that is used by the binding and the database, so you can create an entry in the database, download the XML and have it up and running instantly, but you can also use it to “copy” a definition that exists in a recent version of the binding (where the XML files can be found on GitHub) to work with older versions of OH.
I made this add-on exactly to solve this problem, so it’s a shame if I’m the only one that should benefit from it. It’s a bit too late for you since you already moved to ZUI though.
Combining the add-on with my “Core threading fix” I believe addresses much of the “downsides” to using the native Z-wave binding.