Firstly, the picture quality is WoW! It's the same as OLED TV of LG or Sony. However those are much more costlier when compared to Samsung.
Samsung is terming QLED is better than OLED with respect to pixel burning issue, but I can't comment on that.
QLED/OLED is the latest technology ( CRT, LCD, LED we're earlier generations) . Since it's still upcoming technology, the price is slightly high.
Refresh rate of 120Hz is pretty good, sound is decently good in this model.