I also tried to see the 86" LG 8070 in person and gave up. I viewed the older 86" 6070 and was not happy with the black levels. It was displayed near a Samsung NU8000 in 82" and the Samsung was a much nicer looking TV. When the 8070 came out I found a local retailer that had them in stock, but nothing on display. They showed me a 65" LG 8600 series TV and said this would be the same picture. The 8600 model looked very good.
Went to another retailer, also showing 1 86" LG UM8070 in stock but not on display. However they told me the picture quality would be similar to other UM series TVs like the 6000 and 7000 series, and not equal to the SM or SK series models.
Having no ability to actually see this 86" model in person, I went with the Sony 85" X850G and I am very happy with the picture quality. Black levels are excellent, and while not as deep as an OLED, it seems much brighter with excellent contrast. My only issue is after 6 weeks of owning it, I had to do a reset to get it up and running again. Normally this would not be a big deal except I also have a Sony X800 UBR player and that thing is a mess. Waiting for a replacement from Sony now