I have been using S3 for a couple months now. It cuts good and leaves a good finish like others have said. Only thing I don't like is the dusting I have been experiencing. I use it with a flex 3401 and orange b-n-s foam pad. Am I doing something wrong? Trying to use it too long? Or is this normal? Also wondered how S3 compares to using M105 with a DA. I haven't used it much. Thanks for the help,