Play To hasn't been working for more than a year on my Samsung phone. But I never really wanted to use it, so I ignored it. Although at one time it would list every device on my network, just like Youtube currently does.
It really helps in my household because I have a family member that has a problem using these small remotes, so they use the Fire tablet to search and use Play To... at least for now I am glad the Fire Tablets work. It is so much easier to bring up Channels DVR on a tablet search for a movie hit play to and it is good to go.. I started testing it yesterday and it woke up my FireTV and Started playing the movie it also switched HDMI ports.