I've sailed Disney Wonder twice on interline rates - the first time was a HUGE deal - it would have been more expensive to stay home! I wish they would come out with another deal like that but I doubt it
When we sailed the 2nd time me & my mom (who was with me on the first trip) both received the Silver
Castaway Club gifts. Didn't take advantage of pre-trip planning since we booked close-in.
And the first time was under my maiden name, but they were able to look it up and give me credit.
Just like booking Disney hotel rooms, it's a limit of 2 rooms (or in this case, cabins). And you have to fax your airline id within 24 hours or they could change the price to the original fare. You're also supposed to show your id at time of check in, but I've never been asked for it (always carry it anyway when I travel).
Take advantage of it! It's a huge $$$$ saver!!! (especially when it's so hard to get on flights theses days - it's nice to have a few perks)
Disney has a 1-800 number dedicated to interline booking. If you're on their website and opt to "chat" online with an agent, they can provide it for you.