Cobert said that playing his "Colbert Report" character for 10 years got real tiresome, and that's understandable. If you never watched his old show, his character was a parody of the political pundit blowhard - like Bill O'Reilly. If you haven't seen Colbert on O'Reilly's show you should look it up on youtube - it's pretty hilarious.
On the Tonight Show he's going to drop the character and be himself. Whether or not that works we'll have to see, because he has never done it before. We need to give him a month or two to find his groove.
From what I've heard, it's not going to be your normal late night talk show with 2 celebrities, the latest scandal, and the newest band with a hit. Cobert says he wants to have more 'mature' and thoughtful guests including artists, world leaders, people that make history, etc (he's a history buff).
We'll see.