I have to say Jackson was pretty darn good! He played Sonny pretty relaxed and a 'chill' sort of guy. His timing was really good and he used even his speaking voice really well. His deep, throaty voice on some of the lines was just priceless! I don't really know how to compare him to James or Curtis, he was different enough, but kept to Sonny. He really was awesome.
At one point he forgot his line and said "I need the muse of forgotten lines!" ALl at once the cast said "Cult!" And he said, "Only one, one person!" He continued on once he found his line and was great. He seemed more and more comfortable as the show went on.
Also, the wheels on his skates are tiny, I'm guessing because he is such a big guy. Oh man, he was good. =]
(Sorry for typos...)
Well, I'm glad he got away with it.