LOVETHATMOUSE,
We once transferred a reservation from DCL to Costco not only after we had paid in full, but after we had received our docs. I found out about the deal pretty late in the game, but Costco gave a 10% rebate on the price of the cruise. I called and asked if I could transfer the reservation there, and they did it. DCL was not happy with me, however, and a reservations supervisor called and asked if I really wanted to do this. She said that Costco would now own the reservation, rather than me, and they could make any changes they wanted to. I asked what changes they might make, and she admitted that a
travel agency that wants to stay in business wouldn't make any changes without my say-so.
I left the reservation with Costco, but was really worried that something would go wrong. I called and had them (Costco) fax me a confirmation, since I could not longer look at my reservation on-line. The day before the cruise, when we left, I would stess every time we checked in somewhere (at the airport, at the hotel), and then on the day of the cruise with the bus and at the port. We had no problems at all, so it turned out well, and we saved about $200.
That said, the rebate (which I don't think they do anymore) would be the only reason I would use Costco. I thought their customer service was lacking and it was very hard to get a hold of the agent who I dealt with.