I'm really glad I read to the bottom of this post. While I have used Auto Iso for my D70, then D90, and now D7000, I had never thought of using it in Manual mode. I love shooting dance which is usally poor lighting and fast action - I have done well with this in S, but next I will try M.
By the way - Love Nikonians! Lost interest in DPR because of the fairly frequent abuse some of the members would dole out to those asking simple, naive (some would say "stupid") questions.
Thanks for maintaining a forum with a sense of Values.