I think others have also said this about the new ones. In the Smarthome support forums. They indicated the inductive choke used in the circuit maybe not wound ral tight or not potted to stop the buzz.
Mostly a anoyance problem over a safety one.
If you want to search their site: http://www.techmall.com/default.asp
Another thing I noticed besides the buzz with my new Switchlinc V2's is that the paddles are very loose and one would even stick on or off. I replaced several of the new paddles with the paddles from my old switches, which seemed to work.
The LEDs in the new Rev 2.5 switches are also significantly brighter than earlier versions. Unfortunately this is very noticeable, as I installed a 2.5 and 2.2 in the same box.
I called SmartHome on the buzzing each and failed to mention the problem with the LEDs. With regards to the buzzing, they said that they have been hearing some "rumblings" on this issue and are looking into it. They promised to get back with me once itâ€™s resolved.