We use Costco, which offers a Costco Shop Card for a whopping 8.5% of the base cruise cost instead of onboard credit. You have to spend the shop card at Costco, and since we're not regular shoppers there, we tend to spend it on gasoline at their pump, or electronics.
Since we're executive members, we also get an additional 2% back at the end of our member year. When you add this to the 10% onboard booking discount, it's like getting 20% off the cruise. Worth it for us.
One nice thing about Costco Travel is that you aren't limited to a single agent, so you can call them up at any time you want and talk to someone right away. Their call center is always open when
DCL's call center is open. It can add to call waiting time, though, as you have to call them (& wait on hold to talk to them), then they call DCL while you're on the phone (& you have to wait for that). I've heard waits are bad when new itineraries are released, but have never booked via phone with them on a release day myself.
If you ever plan to use them and don't have a placeholder, I recommend just booking online via the DCL website, then transferring the booking (within 30 days) to Costco, as the savings are exactly the same whether you initially book through them or transfer the booking to Costco.
I booked NCL's Pride of America with them last year.
