Using Millsap to move up to grab Williams makes sense for Utah for the same reason it doesn't make sense for Minnesota: We'd be making room for Williams while Millsap just logjams the 3/4 for Minnesota already.
I would consider moving Millsap to get Irving though. However, again, I don't know why Cleveland does that if they give a **** about Hickson or Jamison.
I really like Irving. He seems the most likely to be a franchise-player in this draft and that's why he's generally viewed as the #1 pick. I really like Millsap too and would hate to part with him, that's how much I like Irving.