I have been in an F10 M5 and I agree it doesn't feel that fast BUT... It is the massive torque and relatively low volume of it. It just turns the dial effortlessly and you just sit there shrugging your shoulders like nothing is happening untill you look at the speedo and realise that you are travelling through time!
Try sitting in it and not supporting your head properly, let your head flop back a bit as it accellerates. You will need to take a neck brace with you for the resulting injury.