For anyone who's interested, it looks like the price on this player has dropped to $150 at B&H, Amazon, and Best Buy:
https://www.bhphotovideo.com/c/product/1317680-REG/sony_ubp_x800_4k_ultra_hsd_blu_ray.html...
Yep, if you're not using Premium Certified HDMI cables with this logo, it's a total crapshoot as to whether or not they'll hiccup passing 4K UHD:
If you're running your video through an AVR, make sure that ALL of the cables in the chain are Premium Certified.
For anyone interested, Crutchfield now has the UBP-X800 in stock and available to ship today:
https://www.crutchfield.com/p_158X800/Sony-UBP-X800.html?tp=171
Most disc players from the same manufacturer have a common remote control code base. I'll bet dollars to donuts that if you plug the codes from a Sony Blu-ray player released over the past two years into your Harmony it'll work just fine with the X800. There may be certain player-specific...