I'm still trying to understand any advantage this service has over Bitstamp or Coinbase.

Does this service allow clients to keep their assets in either BTC or $$ like Bitstamp?
Does the service allow selling BTC and holding the $$ proceeds in their Circle account, like Bitstamp?
Does the service allow selling BTC and depositing the $$ proceeds directly to one's bank account, like Coinbase?
Does the service allow one to sell their BTC for $$ without fees (not sure if Coinbase charges a fee upon selling)?