Just got my second U36JC after the first got replaced. This one has a problem that I didn't experience with the first one: when you turn the screen back on after it's been automatically turned off, the screen is usually glitched.
The artifacts disappear, after something has been dragged on them. Nothing really drastic or something that would turn the PC unusable, but it's nevertheless annoying.
A completely different subject, but sometimes when connected to internet through wireless connection, the internet disappears, and you have to reconnected the WLAN to get it back. Never had this with my old crappy PC.