JOEL - The big difference is that the LDS Church has prophets who can, through revelation from God, properly interpret the scriptures for us and receive additional information from God about this subject. We have additional scripture from God that explains Eternal Progression in better detail. And LDS members also have the constant companionship of the Holy Ghost to help understand these things and recognize the truth of what we read and hear. Actually what we believe is not polytheism. More precisely it might be called "henotheism", which is defined as "the worship of one God without denying the existance of other Gods" (Websters).