Ken Jennings, I thought, was really good. Buzzy was overly enthusiastic for my tastes. I thought Mayim Bialik was suprisingly good. I didn't like Katie Couric at all. Mike Richards was just....lackluster, I guess is the best word for it.
Yes, I know it is extremely picky to not like Mike because he was "lackluster" but not like Buzzy because he was TOO enthusiastic. I'll defend myself by saying that there is fine line, and walking that line is what makes a Jeopardy host great. Not overly dull, and not overly excitable.
"We are not provided with wisdom, we must discover it for ourselves, after a journey through the wilderness which no one else can take for us, an effort which no one can spare us, for our wisdom is the point of view from which we come at last to regard the world." --M. Proust