I have used this service for years and have run into my first problem.  The withdrawal that I scheduled three days ago was fulfilled with transactions using too small a miners' fee given the current transaction pool.  These transactions are still unconfirmed three days later.  I have messaged support through their site but have not yet received any response.  I am posting here as a warning to others.  I will update this post if I hear back from them.

Edit:  After four days, the transactions did confirm thanks to a magnanimous miner.  I still have not received any response from the Bitcoin Fog 'crew'.  I will be using a different mixing service from now on and advise others to do the same.