Believe it or not I used to watch David Letterman while studying for my varsity exams. I aced the exams - so not sure how you would rate the show given those stats...just that I really enjoyed having that sort of "noise" in the background! ;)
I never miss David Letterman - I am so going to miss him when he goes next year - I wish time would stand still. I also never miss Jimmy Fallon. And so wish we could still get Jimmy Kimmel here in Australia he is even funnier to me than Fallon. But really I watch any of the ones the show. Big fan of Jon Stewart and Colbert.