If you take you home at the moment there's the threat is very minor. But if you look a tad further into the future, where most of the stuff in your house will be connected, the devices are
Depends how much you want to get into it, if you look outside of your house at say road signs, traffic lights, etc. an attack on those can be quite devastating. Back on a privet/individual level, if a denial of service attack is sent to you garage door which doesn't allow you to leave the house when you're in a rush to get to work, or doesn't let you unlock the door to get into the house, it's not horrible but quite a nuisance. Add to that an overwrite to the garage sensors, allowing the door to close whenever it feels like it and you gut a ruined car or a hurt animal.
In my opinion it can be as big of a threat as someone will make it. Depending on the amount of IoT we have around us and our dependency on them, as well as the levels a hacker's imagination and the length they would go to.