Picture and sound quality is excellent. TV is used primarily for gaming and watching movies and sports and love it. We now have three X900F in different sizes (85", 75" and 55").
I bought the Sony XBR55X900F on 10/13/18 replacing my 2013 XBR55X900A I'm extremely happy with the overall performance and picture quality. The only thing I had to sacrifice was my 3D.
I bought this to replace a 15+ year on Sony. Was easy to set up, including installing the stand. The picture is awesome, almost looks 3D. I do not use all the features of the TV, such as the voice, as it is connected to a satellite dish.
I replaced this tv from an entry level LG 4k tv. All I can say is WOW. I did not know how great 4k and HDR could be. The dolby vision on netflix is incredible. The 4k channels from direct tv blows my eyes away. The clarity and bright and contrast is beyond this world.