I just checked my 42PX50U and it has 5185 hours on it. I bought it just over two years ago (May 20, 2005).
Time is 1441 hex = 5,185 hours, an average of 49 hours per week which is less than i thought considering i don't watch a lot of TV. I do keep it on as backround noise when doing other stuff around the house though.
Count is 00BB5 hex = 2997 times it's been turned on, which is an average of 4 times per day (sounds about right)