I was concerned that a HDMI switch would not work with Apple TV having read many horror stories about how temperamental switches can be and how the Apple TV does not drop its signal which can cause problems. There was no need to worry because this switch just works like magic!
I bought this model because it has a remote in case the automatic switching did not work and also bought the 5v POWER SUPPLY For Neet® Switch - Neet® Lifetime warranty
in case that was needed, but it turns out that I didn't need either - everything just works like a charm.
It comes with good instructions explaining how to deal with problematic devices etc. I connected the Apple TV to input 1 following this advice, and a DVD player to input 2 and it works exactly as I want - the DVD player overrides the Apple TV if both devices are on, and the right device works if just one is on. I have tried this out with 2 different TVs (a Sony and Philips). Everything works as well as if they were on 2 different ports. I got this for my mum in her 60s and am confident that it will keep working without issue and she can just use her DVD and Apple TV without knowing anything about a switch.
Just remember that you will need an extra HDMI cable when using the switch i.e. a cable for each device and then a cable from the TV to the switch. This sounds obvious I know, but I forgot until I had everything in front of me to set up and was a cable short :)