Well, Kikuchiyo is insane but yes, Katsushiro's the most interesting. Of course some of them don't have very distinct personalities... Kikuchiyo, Katsushiro, and Kambei are really the only ones I can identify without question...
"Of course some of them don't have very distinct personalities..."
I suppose having multiple Japanese names all beginning with "K" doesn't help make them any more distinct :) Which part are you at?
Let's see, there was the Kid, the Old Campaigner, the Wild Man, the Swordsman, the Cheerful Guy... uhmm, the guy chopping wood, the guy who made the flag... were those last two different people, or were one or both of them the Cheerful Guy? Oh, yeah, there was the Old Campaigner's buddy, too, the guy with the spear.
Is that seven?