@mstormi, When I did the 2.5.2 apt-based install, I didn’t migrate anything at all… it was completely clean, down to a fresh OS install, using zwave discovery from scratch, and no other addons installed. So, I think I can reasonably rule out any contanimation from old configs or other addons…
What I’ve done is taken crazyves’s direction (rebuild) and gotten a new ZWave stick, and selectively moved a few devices from the “unhappy” stick to the “new” stick. I see the expected (instant) response on the new stick with the devices I’ve moved over.
It looks like I can leave the old stick in as well (making three, total)… the devices what I refer to as the ‘new’ and ‘secure’ sticks work well, but the devices on the old stick still have the ~600 second delay. So, I’m in the process of moving the devices I can get to (which are the important ones from a latency point of view… the light switches, etc) over to the new stick.
Since the devices that I can’t get to are mostly power meters, and they still seem to report on schedule, I’ll leave them on the old network/stick until I can physically get to them to move them.
Not a great solution, and I’m still convinced that there’s something out-of-spec with the network that perhaps the binding isn’t handling well as it could (based on the behavior differences between the 2.1 and 2.5 bindings), but I guess I can close this as an active question, as I have a functioning install at this point… thanks for everyone’s help!