I'll say it too. TK was TERRIBLE on MNF. It didn't take long at all for me to get tired of the lame corny jokes that he made all the time. He just wasn't a good fit, period. I almost decided to just watch the games on mute.
I liken Kornheiser in the booth to having a circus clown there every week. When he stretches for the entertainment value in his opinions, it weakens the broadcast simply because he just isn't very funny. Ultimately, that makes a mockery of the game. It's alright to inject humor when it's subtle, slightly colorful, and adds to the actual game. But Dennis Miller and Kornheiser in the booth were both experiments gone bad before they even started.