It's my opinion that Nancy Barrett gave the most consistantly excellent performances of any actress on the show. From spoiled teenaged Carolyn, to demented old Carolyn, to loopy Pansey Faye, her characterizations were uniformly excellent.
I never saw the pairing of Karlen and Barrett as the embattled husband and wife, William and Carolyn Loomis, until the last Sci Fi run of the show. But after watching them play those roles, it seemed to me a terrible waste that the two actors never got to play "Who's Afraid of Virginia Woolf" on stage.