My Samsung PN64D7000 is going back this week too, and also because of buzzing. It's too bad about the buzzing too, because watching The Lord of the Rings trilogy on Blu-ray was nothing short of amazing on that TV. Maybe Samsung will actually try and get it right in 2012.
Input lag is hard to deal with on the LCD side but the 2011 plasmas all have problems of one kind of another. I'm keeping an eye on the Samsung UN60D7000 series and waiting either for a mind-blowing announcement from someone at CES in 2 weeks which makes me forget that TV, or a great deal before the Super Bowl.