Good question!
I have not found how to withdrawal bitcoins...
Edit: just paste the bitcoin address. It's so easy that I had not figured out how to withdrawal.
Edit 2: fees are 100 "bits" (0.0001 BTC) for each movement (fund or payment or withdrawal)
I'm really not sure how I feel about the 100 bit fee on absolutely everything. That could add up to a lot over time. I'd rather have a higher withdrawal fee and no transfer fees, really.