From what I remember reading before I purchased the parts, the BeQuiet cooler does not have it's own regulated fan setting - it connects directly to the motherboard and relies on what setting the motherboard gives it. From what I have experienced though, it seems to run at 100% all the time, even when idle. I don't mind though, as it only runs at 1500rpm and it is very, very quiet.
Definately the quietest CPU cooler I have ever used and with the temps I have been getting with OC'ing, I would recommend this cooler again. Indeed it may not be the best cooler for when OC'ing but say for someone else doing non-extreme OC'ing like me, it definately is more than adequate for the job.
Bulldog - the only explanation I could give regarding what you said is that your using a Gigabyte board. Just saying, as I am using an MSI board.
Liam