I grew to like the rasp from the E46 M3. But, having said that, I like the sound of the V8 exhaust much better. I'm still stock (hoping that will change soon) so I hear no rasp at all. I have no clue what causes it though. Also, FWIW, the Z4M had the same engine as the E46 M3 yet hardly any rasp compared to the M3.
I've been assimilated. 6MT/ZPP/18"/PS extended.