This is sort of related to Nils Frahms recent release –solo–, which was recorded on the M370, and of which all proceeds are donated to the construction of the Klavins M450 piano[0].
This is nice so far, but I wish they had found a way to record with less white-static and it would've been really impressive.
Are you referring to the hammer mechanism clicks? (They're rhythmic, along with the notes, as opposed to random noise.) I think the exposed mechanism makes that sound more present in the recording. The outer body of a conventional piano serves to muffle that.