I have mixed feelings on Ferguson in Letterman's stead. On the one hand, I think his show is good and it's the only one I can stand on the regular. On the other hand, I don't think he'd be able to get away with his style as much in that spot and it wouldn't appeal to as wide an audience.
Of course no one cares what I think any way and I don't think he'll be up for that spot any way, but just my take. It's funny that Seinfeld pitched a similar show about "nothing", but I feel like that describes Ferguson even more. A talk show about nothing. Good show though.