For anyone thinking of getting this TV I can report that first hand its bloody great.
I upgrade from a few years old top of the line local dimming Phillips (40PFL9705) screen and I was concerned about how black the blacks would be. After having used this now for more than I week I'm over the moon with the picture quality.
There are lots of grumbles about Android TV but again talking from experience I'm finding it to be generally very good. There is the occasional wait if changing from one app to another, but nothing unexpected.
The one massive boon on this however is Kodi, having played with a MinixNeoX7 for ages and using this for my media I was worried about the power of the TV to run Kodi.. I had nothing to worry about, its super fluid and very very responsive.
For £950 for a 4k very smart TV I'm really pleased.
Sony KD-55X8509C User Review
Great 4k TVReview of Sony KD-55X8509C tv by billytkid, Dec 14, 2015.
Contrast/Dynamic Range/Black Level9
2D Picture Quality9
3D Picture Quality9
Picture Quality Calibrated9
Ease Of Use9
Value for Money9