I personally cannot stand Jimmy Fallon. He's just so unfunny. And he tries so hard. I'd put him just slightly above George Lopez.
That said, if DT actually did get on JF though, I'd definitely watch it. I'll support them regardless.
Question though, with JF does the musical guest just sit in with The Roots? I mean, that'd be cool and all, but I don't think that would get DT the recognition they deserve. That'd be fantastic once they already had a bit more mainstream recognition. But to get that they'd have to expose a whole not audience to their music.
Also, pretty sure Conans currant show wins for guests. I mean, he had on Tim and Eric. And it was the best thing ever.