My parents only ever thought that Letterman was okay. My dad is a huge Leno fan. It was disappointing because he came to Baltimore when we were in WDW in January, otherwise my mom and I would have gotten him tickets to see Leno.
I don't think it was really Leno that stabbed Conan in the back so much as it was NBC that stabbed every one of them in the back. That network is not too bright.
As a sidenote, while Conan seems like a perfectly nice guy, I cannot stand his humor. We'll be watching Big Bang Theory, and as soon as Conan comes on, we flip it off as quickly as possible.
I've never really watched Kimmel. If I'm going to watch late night TV now, I watch some of Fallon and then flip to Golden Girls reruns.