I know that most random generation uses mouse movements and hardware activity to create entropy.  However, I like the idea of being prompted to move my mouse for a period of time as it confirms that the software is doing it properly and not using some poor function to provide randomness.  It's one of the reasons I like using truecrypt for data encryption.  I am sure most bitcoin clients like multibit, bitcoin-qt, electrum etc...use mouse/hardware activity but since I can't confirm it I roll dice when generating new addresses.  It's a pain, but at least I know I am getting true randomness.  Anyway, cool site, the only thing I would recommend is maybe placing a textbox displaying the random pool as you move the mouse.