I have just received my copy of PG349 yesterday, but the grey uniformity was bad.
There is a dark zone of 1cm thick across the entire top part of the panel. I have contacted the local Asus service team for help, and a picture was sent to them for further analysis, no feedback atm. I don't know whether this is consider as "normal" or not, but I am surprised by the uniformity of a monitor at such a price.