I have two apple TVs and have had very poor experience with HomeKit so far. I've reset my entire homekit setup twice now and it's still not working very well. I've noticed that when the Apple TV is not asleep, I'm able to control my home kit enabled door lock just fine over wifi and over LTE when I'm not home. As soon as that sucker goes to sleep, I have issues 99% of the time. The ATV is about 10 feet from the home kit device.
Not sure if others have experienced the same. Keeping the Apple TV from going to sleep is not a good option either since I have it set to turn my tv and home stereo on/off (one of the touted features of ATV4).
Hoping the next OS update makes some improvements but I'm not so sure. So far HomeKit has always seemed like a half-baked solution (probably why this hasn't really been covered much at all during recent Apple launches).