On my new 500M, with Power Save modes off, there is some panel buzz but it is about the same as my older 4280 and really doesn't bother me that much.
That said, I have been thinking all along that (even with the D-Nice settings) the 500M is still a bit too bright in the brighter areas (compared to my previous 4280) for my dark basement. (The dynamic range of this panel really is amazing!)
I tried the Power Save 2 mode and I really like it!
This goes against everything I have seen in the settings threads and I did not use any of the power save modes with my 4280 but I am really liking the the way the picture looks with Mode 2 on my 500M.
As a bonus, the panel is totally quiet.