Recently, there was a thread started on this subject. I think it was down in the Tech support forum.
Regardless, I don't think there were any details about the benefits of a premium membership.
I am looking forward to reading about that.
I already have one area of concern: According to the information in the mast head, the membership will renew automatically without prior notification unless the price is raised. The benefits would need to be quite outstanding in order for me to join with this policy in place.