From my personal use, I've found at home that the Sony and Samsung TVs I have the HDMI-CEC works flawlessly. When I've tested with some small insignia TVs it never worked properly. I have a 7-8 year old 26" Sony LCD in the bedroom, only thing connected to it is a new Apple TV and am quite happy that I only need the Apple TV remote now.
In our family room, we have a Sony AVR and a Samsung TV connected to the AVR (along with a new apple TV). Works flawlessly here as well. Hitting any button on the Apple TV remote wakes up the AVR and the TV, sets the correct input, and AVR volume is even controlled over HDMI. Sounds stupid, but it's one of my favourite things about the new Apple TV.
Lastly, in my basement, I have a new Apple TV hooked up to a 2015 70" Vizio TV. The Apple TV can turn on the Vizio, but it never sleeps it properly. There's a thread here on the subject actually from last year.
Stupid enough, this is one of my requirements when looking for a new TV. So convenient. Honestly, if you find an inexpensive Insignia or other less-known brand, doesn't hurt to try it out.