Eh, I've only watched the first episode, but I wasn't a fan. A lot of the special guests have simply not been funny, but if the alternative is getting a guest (Lauren Cohan) and not letting them say anything other than the closing credits, then what's the point? They should actively be seeking funny guests and then letting them be funny, instead of just being a prop.
As for Ms Tyler, you shouldn't have to say "Welcome to Whose Line is it Anyway?, the show where everything's made up and the points don't matter" after every single commercial break or game, and her voice was irritating to me. I like that Drew and Clive would dig at the others, she just sort of seemed like a fan/observer. I hope that things pick up, but it's not as if they have to experiment with a new format.