I liked Letterman a lot in the 80s and early to mid 90s. But then he got stale. Same ole, same ole, over and over again. Still far better than Leno though, who I truly despise both as a human being and a bland, unfunny so-called comedian.
I would still watch Letterman occasionally and felt he was the best late night guy until Fallon came along. The remark about Palin's daughter was in fact pretty low, but I was more disgusted by the video of him having sex with an employee.
Still and yet, I watched the final show and enjoyed even though I had not watched him in a few years. I appreciate the laughs he did give me, and he is a Hoosier so there's that.