This has a lot more going for it than the Roku 3 or the Apple TV, but there are also some downsides. For one, the Roku 3 remote has a headphone jack, while this one has a microphone. I just bought a Roku 3 for my parents and my father is hard of hearing. He uses the headphone jack and my mother maintains her sanity.
Actually, I think that's the only downside that I can think of, but feel free to add more if you can think of them.
I'm psyched about the integration with the Kindle Fire HD, the gaming capabilities (With $40 controller option), the increased storage space, and the microphone search function. Definitely going to give this one a try, because I was about to buy myself a Roku 3 after how much I liked my parents'.
On the bright side, the controller comes with 10 dollars in games and Sev Zero. Not exactly a steal, but helps ease the pain of the price point.
They also designed and built their own game controller, which honestly isn't half bad.
4 Players according to the promotional video on Amazon's page for the FireTV.
EDIT: My bad, they mention it on the promotional page for the controller, not for the TV. You can find it here: http://www.amazon.com/dp/B00DU0ZI8Q