Yes, i asked the pass bureau this very question a couple days ago. Your travel benefits don't change for the first 30 days, after that you go down to S3B. Your parents, spouse, children, travel companion all become/stay at S3B and pay a yield fare. Buddy passes remain the same. You lose all interline travel, including travel on Northwest..and obviously jumpseat privileges.

I might be incorrect about spouse and children paying a yield fare. The pass bureau woman said only the employee rides for free and everyone else pays the yield fare, if i remember correctly. I don't have a spouse or kids..so i didn't ask any more questions about that.