Hmmm .. some good to know info there!! 
Just one thing, your article states that the PWM on the Arduino is based on the external crystal frequency e.g. 16MHz. I thought it was +- 490 Hz by default as per the wiki analogWrite() - Arduino Reference?
BTW, how does one decide on the correct frequency for a brushed dc motor? From what I have seen most folks recommend +-100Hz for simple (open loop) applications? :-? (Question moved to FAQ section ..)