Using the on/off state of the TV to control lighting is very satisfying. Automatically dim the lights nearby the TV that otherwise give reflection etc.
Currently there is no apps that supports my philips TV. Then instead I added a power plug to detect the power usage. Tracking when the TV passes 5W seems to be reliable.
With home assistant I had support for apple TV, and was able to increase the lighting when the movie was set on pause, and then dim down when I hit play. I'm not able to do that with just the TV state, and I hope someone adds an Apple TV app anytime soon.