I dont see a spinup/spindown setting for a func_rotating. This is what it says at VERC:
"fanfriction (integer) Friction (0 - 100%) (default: 20) - This modulates the spin-up/spin-down rate of any brush that uses the Acc/Dcc flag."
"16 - Acc/Dcc - If this is enabled, the object will accelerate to and decelerate from its maximum speed based on the Friction value."
This doesn't seem to work, unless there's something I'm missing.