I think it was funny for the first season - but after that it made me feel uncomfortable watching it. I'm just not a person who likes surprises. Nor do I find Ashton Kutcher all that entertaining. His "oh man, I am sooooo clever and wild" schtick wears thin easily.
As a side note, I went to Target a while back and saw two guys with Punk'd shirts on and Ashton hair. Annoying.