Yeah, s/c whine is one thing but belt rattling is something that you wouldn't like:
YouTube - vortech rattl*
I hope STILLEN kit will not suffer from the same issue.
[EDIT] I eventually watched the above posted video, the rattle is clearly audiable there as well and it sounds like a jet at idle - not everyones taste and not subtile for sure. STILLEN screw-type charger for 350Z was the exact opposite and OEM-like solution (except the hood cowl).