I don't think it helped the fuel ecomony, but it was hard to tell because we also had a chip in that combine. As far as being harder to startup, our cylinder belt and variable speed belt probaly lasted longer because there was no more slugging when doing wet heavy swaths.
On another note our neighbor has 3 machines with the sunnybrook setup. He had a keyway go on one of the beaters during harvest so he just put the JD one back in. He couldn't believe the difference it made, so after harvest he fixed the sunnybrook back up and put it back in.