Many people never notice it. Lots of LCD TVs today use PWM. Actually, it's mostly visible when not looking straight at the TV.
It has been quite a big topic for PC monitors for a few years now. Personally, I've stopped using PWM-based PC monitors some years ago and I felt that it relieved eye strain at the end of the day. We've written more about it here if you are interested:
http://www.flatpanelshd.com/focus.php?s ... 1362457985