I'm using home assistant with thermostats and humidity/temperature sensors mostly to get information how the house heats and how the rooms are affected by humidity and temperature changes.

I also automated two dehumidifiers with those sensors and zigbee plugs to not run 24/7 but in defined windows when the noise isn't bothering anyone and if the humidity triggers certain thresholds. The automation also has hysteresis sesstongs so the devices do not constantly turn on and off.

In general I don't automate to a point where I can just flick a switch or turn on something manually. But it is nice to be able to control and see everything.

Here is a list of some practical uses so far:

• Get a notification on the phone when the washer is done.
• Charge the car when electricity is cheap
• Turn on humidifier if sufficiently humid and no motion near it for a while
• Automatically lock the front door at night
• Toggle lights with a shortcut key on the keyboard
• Change target thermostats for different rooms and different time of day.

Also nice to learn about the house:

• Breakdown of electricity usage. (How much actually goes to heating, car, etc)
• Answer questions like "When did I really go to bed last night?". Etc

What I really want is a smart home that tells me that the stove is on and been unattended for over 20 minutes now.

And which can tell me which when I went to bed last night.

Obviously it would have to be offline not some crowd service lives streaming to the NSA.

I do it mostly because I'm forgetful. So I automate what I forget. For example I always forget I've put the washing on so I get repeating alerts to hang it out. The alerts stop once I've scanned the NFC tag on the washing machine.