My Thread devices are all HomeKit devices, and they work incredibly well. Once they are joined to the Thread network they show up as IPv6 devices in mDNS and just work.
I have a ton of Thread enabled lightbulbs, smart outlets, and sensors on Thread, and I haven't had any issues.
They seem to mesh really well, store and forward for devices that are sleepy just works, but sleepy devices waking up and sending traffic is almost instant.
I do not own any devices that use WiFi, other than my Ecobee thermostat. So I can't compare against that. I would put the Thread devices up there alongside the Zigbee devices in terms of reliability, if not more resilient since I have multiple thread border router capable devices (multiple HomePod mini's and Apple TV's with Thread) so a device getting restarted (unlike a Zigbee hub like Hue/IKEA TRADFRI) won't affect the network/ability for the devices to trigger responses.
