Given what I had heard, I was surprised at how much I enjoyed James Hall's performance in his 4 or 5 episodes when I screened them last year. Despite his difficulties with the line readings, I thought he had an interesting take on Willie. Very creepy--just watching him in his scenes with Vicki practically had me biting my nails (not something one is wont to do under ordinary circumstances).
I dont't think there's any question as to who is the more skilled thespian of the two. Karlen obviously stands head and shoulders above his predecessor. But I also don't think it diminishes Karlen's achievement in the slightest to note that Hall did a better job with the role than common fan wisdom would state.
Someone asked one of the surviving cast members in NYC last year while Hall was replaced, and she answered that he had a drinking problem and was told he would have to go "but in a nice way." (laughter from both the stage and the audience)
G.