Here's a quick review that I have after using my X90J about a month or so:
Pros:
Lovely colors out of the box. I didn't change any display settings but it's very good for me. Also take note this is my first 4K TV so the experience might varies from people to people.
Can Airplay with iOS devices.
If you like photography, you would appreciate on the shots taken by Sony DSLRs. The pictures are available something like a screensaver on your TV.
GoogleTV as OS.
Cons (again, if you don't look for the issue you wouldn't even notice it):
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At certain angle, I would notice my room light reflects on the TV.
I think the blooming issues is apparent when turning on subtitles while watching movies/series that have letterboxing. Every time subtitles comes up the lighting of the screen would change a bit, even on the top half of the screen.
Wifi connection suddenly could not turn on. Need to restart TV to enable it back.
No Bravia Core
May add something else if I notice anything else in the next few months of usage/explore.