I would say that a AUTOMATIC FAIL OVER INTERNET CONNECTION menu/feature will be nice to have. Not only using the option of two default gateways but also having automatic fail over and load balancing as Nexland Proturbo or Hotbrick DSL agregators have.
You can use netwatch to do automatic failover – search the manaul.
We will have feature settable at the gateway for this in the future – basically checks if the gateway is still reachable. Though this doesn’t guarantee that your the internet is reachable further – for this netwatch is better.