I've inherited priority boost a number of times (im a consultant) and every time the DBA/Techie that turned that option on
did it without knowing what it does. "It sounded like a great feature".
So far i've blindly followed Microsoft (and everyone else) instructions and just turned it off. Have not measured any impact afterwards.
Never had a problem when turning it off (SQL 2005, SQL 2008 and 2008 R2).