I had two 5010's and both buzzed loud. My new 5020 has no buzz unless my head is behind the screen. The 50 inch 9g's must have improved on this issue. My second 5010 is a April 2008 build and my 5020 is a May 2008 build, so this leads me to believe the changes in the 5020 result in the elimination of buzz.
Reports of buzz on the 60 inch 9g's make my assumption questionable. The 60 inch screens, due to their size are more prone to buzz, so maybe the 9g's fixed the 50 inch buzzers but the 60 inch screen are a whole different set of problems because of their size.
Just a note: I compared both the 5010 and 5020 in the same room and same set-up.