A few people have been scammed on the site, Only use paypal to pay for items for sale by other members. If they will not use paypal, its likely a scam NEVER SEND E-TRANSFERS OF ANY KIND.
Sounded noticeably quieter to me with baffle open or closed, at least as much a difference with a normal GP exhaust and a baffle/no baffle set up. I think it's a great little gizmo
Too bad it won't retrofit into an existing Carbon GP though.