FWIW I looked at the Samsung 55JS 8500 ,Sony 55X810C and Sony 55X850C 4K sets for the bedroom /PC executive office desk space and picked up the Sony XBR 55X850C for $1199.00 on sale SAT 11/28 .
My view distance is close in the daytime ~4ft at the desk and ofc further back in bed at nite .
I use the TV for an extended PC screen and for movies,sports and TV ,Dish and OTA and Roku and the TV Android apps and embedded Netflix and Youtube 4K .
The 4K works well at the desk with the TV adjacent to it on a full motion wall mount ofc it probably doesn't hurt otherwise with all that comes with it on *this set * especially the WCG .
The XBR 55 X850C has excellent upscaling and good picture once you tweak it a little ,and ofc Sony color .
The Triluminos WGC ( bt2020 and DCI modes ) they can add to [ good 1080p bt709 content ] and make it better sometimes . I would expect similar results from a Samsung JS8500 .
The Samsung bt709 4K JU 6500 and sony X810C.s look to be decent when on sale @65" and under if you don't want their SUHD or Triluminos WCG ,........The JS 7000 SUHD maybe not so hot ?
OTOH on the X50C turning on HDR luminance usually doesn't work well on 1080p bt709 content .
On a bigger set over 65" the price increase /value on those 4K sets is more of a consideration considering the current state of affairs with HDR luminance content and all ........ YMMV .
Decent 1080p sets are hard to find at all now unless you want a Vizio or something like that
that may not be bad for the money in the 1080p 65" and larger sizes if you want to wait on 4K/HDR + WCG.
At 55" and 65" I'm good with the 4K Sony X850C Triluminos WCG with HDR support and Samsung likewise 4K SUHD JS8500's YMMV .
So to answer the OP's question is a 4K set worth it .........I would say.......it depends ..
OTOH .for me the 4K WCG and sorta HDR is worth it for me in a 55" if something else knocks my socks off in a few years I'll flip this for whatever that might be anyway .
OTOH I'm not looking to see OTA bt2020+ HDR ( to much bandwidth ) or all that from Dish or *DTV 4 K lite they cant even get 1080p right half the time ,OTOH the more doable bandwidth wise WCG DCI is already in the Sony X850C and the SUHD JS8500 ??
I played a bt2020 4K WCG demo loop @ 25MB/s today from an usb hdd into the new TV it was beyond excellent and way better than any of my 1080p sets could do (color and detail ) with the same file downscaled to 1080p in the PC dGPU.
Here's a link to that eye candy download
http://demo-uhd3d.com/fiche.php?cat=uhd&id=34