A Ustream Premium Membership allows you to view streams without ads and browse the Ustream site without seeing any banner ads. If you are a broadcaster, your viewers still see ads. A premium membership only allows one person (the premium membership account owner) to view without ads while this person is logged into their premium account.
A Pro Broadcasting account allows you as a broadcaster to deliver a stream to viewers without ads. Pro Broadcasting is priced based on how many people watch your stream and for how long they watch. This measurement is called "viewer hours." Even if you only broadcast one hour, if 10 people watch for the entire time, then you have racked up 10 viewer hours.
Producer Pro is a desktop broadcasting application that allows you to broadcast to Ustream. It has no relation to ads on your stream. The only way to remove ads from appearing on streams you broadcast is through a Pro Broadcasting account.