I don't watch much television and up until recently I have been what you might call a loan family historian - basically doing everything on my own and not following genealogy news or what others were doing.
Therefore I did not hear about "Who Do You Think You Are?" until the beginning of the current season.
I have read some criticism about the show along the lines of "it's bad genealogy" or "they don't show enough of the research". I think that the reason is that some people who are watching the show are missing the point. This show is not about genealogy. It is about family history.
Quick Amateur Family Historian definition: genealogy is how you find information about your ancestors; family history is what you do with that information.
While I thoroughly enjoy seeing original documents that are sometimes hundreds of years old, the best part of the show for me is when the person shares the results with their family.
I like the show so much that I bought the first season from the iTunes Store. I may comment on those episodes as I watch them.