Have you verified that the HDMI port you're using supports 4K/the nessesary HDCP? I stream netflix directly on my smart TV (as well as youtune 4k), and like I said, the difference is immediately obvious. I suspect you're getting 4k downscaled to 1080p.
It's definitely working -- in fact, the FireTV won't even display the "4K Ultra HD" categories unless it's connected correctly to a compatible TV[0]. I notice the difference if I actively try to, I just don't think it's as mind blowing as everyone is claiming it to be. It's certainly not something I couldn't live without.
