I've replaced all of HA with just some Python interacting with an MQTT server. I just script all the automation and don't have to care about the other 90% of what HomeAssistant brings to the table.
Not for everyone obviously but it's simple and works well.
I haven't because what's described didn't really suit my needs. I can run my own daemon that will handle the integration with MQTT, and that's all I needed.
Not for everyone obviously but it's simple and works well.