Actually, I think the "rust" issue has been put to rest on acadiaforum.net - I believe that it ended up being one person who had rust, which means he got a bad exhaust somehow. All the other posts about "rust" turned out to be normal stainless steel discoloration caused by the heat in the exhaust, which is completely normal. The only "issue" is that, because of the high rear deck, some of the exhaust is visible from behind the car and it doesn't look great.
A few users there talked about using rubbing compounds to remove the discoloration, purely for aesthetic purposes.
A few users there talked about using rubbing compounds to remove the discoloration, purely for aesthetic purposes.