Having built a more refined FD, I've got to say I enjoy the NA 20b a lot in Gentlemen's Express clothing. I think this is exactly what Mazda should have made in the first place and charged another $5-10,000 for the car. It sounds like it would if the factory had made it. This is still break in miles, so I held it under 6,000 rpm and don't go WOT ever.
At cruise its very quiet. Going up or down through the gears it sounds very musical to me. Although its hard to hear on the video, its reasonably loud under acceleration, but not too loud. Not an unpleasant sound. I was willing to live with the power trade off to make this more civilized. The sound of a p-port motor at 2,000 rpm idle going rumpityyyy-rumpityyyy-rumpityyyy isn't what I wanted. I wanted a pure rotary soundtrack, if you know what I mean.
http://www.youtube.com/watch?v=3DfLd-D5VBg
Gordon