`establishing it as a more robust foundation for larger and more heterogeneous deployments.` Based on.... 6 devices? Quite honestly I would have been interested in measurements with more than only 6 devices. Maybe upto 50 or so,even better if they'd mixed different hardware nodes for a more realistic scenario
It's not as fast as Zigbee, not in day to day usage, and not in terms of reconnecting, which often takes 30 seconds (ie. after a power outage) where my Zigbee devices just seem to reconnect instantly. On day to day usage there's a slight delay when turning something on, but it's maybe 100ms or less.
I initially had quite a few problems, but after "standardizing" on a single thread network (I had 3 before for some reason), as well as adding some wired thread border routers, things have become much more stable.
My zigbee to thread is still a "work in progress", replacing devices as they fail (ie. lightbulbs), and I'm also still adding new Zigbee devices like the Aqara T1 Valve controller, but I prefer thread over zigbee today.
One thing I will note, people tend to underestimate the range of thread (and zigbee for that matter). Each mains powered device will function as a repeater just like zigbee, and I initially thought I might need a couple of smart plugs as repeaters, but despite having a somewhat large house (by european standards) as well as double brick walls dividing it, my thread devices have no problems "seeing" a thread border router in the opposite end of the house.