Miles really has shown me nothing except that he is nowhere close to being an NBA quality player right now. He has not brought anything (offense, defense, or hustle). It is clear that he just is not ready yet, and who knows if he ever will be again. Right now, I think he simply needs to be the cut. They can always try to resign him if he ever gets some more of his explosiveness back, but as of right now, he is the least effective player on the roster (and yes, that includes Scal, who is MUCH better defensively).
As for Giddens, I liked what I saw of him last night. He reminded me a bit of Pruitt last preseason, in that he looked lost, but he showed some very good defense, hustle, and even made some nice passes. I think he needs some time in the D-league, but eventually, I expect him to be a player in this league.