I have half dozen Hue bulbs, and they seem rock-solid - far more stable than my Lightify bulbs.

The HA SkyConnect does seem to be a factor. For a while, my Lightify bulbs were the last thing on my old Samsung SmartThings hub (via the HA integration- basically using the ST hub as a Zigbee radio/stack), because they operated more reliably there.

Yes, every line-powered device is (probably) a repeater. Many light bulbs are, with the caveat that you must keep them powered all the time. Having a bunch of repeaters drop offline will cause fits with your mesh stability.

Make sure to look for Zooz blueprints - there are blueprints for many switches. The blueprint for the Zen32 scene controller really helped me use the switch to the full extent.

Zigbee is notorious for mesh instability, mostly because some devices (looking at you, Lightify) are picky about what repeaters they use in the mesh. Build your mesh slowly, spread some good repeaters around your house, and give the mesh time to settle down before using it in production. Don’t move repeater nodes or power them off. (I had some lights that I had to delete and re-add every two weeks, until I figured out that the cleaners were unplugging a repeater to plug in their vacuum:-) Finally, make use of the “Visualization” tab under Configure to see what’s happening on your mesh.

I’ve had a couple of Kwikset 920 Z-wave locks and they are solid. All local, good integration with HA security, no phoning home.

One of the features of my Tempest PWS that is a real blessing over the summer in lightning detection. My rescue beagle does not handle thunderstorms well, and the vet recommended some anti-anxiety meds - but they need to be given well before the storm is audible to some very large ears. So, I have a Home Assistant automation that sends alerts for > 5 strikes within 60 miles.

You can also get the Blitzortung integration for Home Assistant, which will let you generate an alert from their cloud data.

Is there any difference in network performance, e.g. reliability of communication, or is that all down to the hardware?