Let's not get things confused here. DME is a wonderful service and one that works quite well. BUT....DME is not the same thing as the RAC system at the resorts. This (RAC) is a system where you can check your bags through to your home airport, right at your resort, on the day you checkout. Then, they will print out your boarding pass at the same time. It is the exact same thing as checking in at the airport! BUT...it is only open to people flying on a select group of 'participating' airlines. These can be found over on the Transportation board, in a stickie at the top of the board.
If you are not flyng home on one of those 'participating' airlines, you will just take your luggage with you to the DME bus. The bags will be stowed underneath the bus and you will take it to the appropriate airline counter to be checked and to get your boarding pass issued.
Although the CM's working the RAC counter wear outfits that say DME on them, they are not truly DME. In fact, anyone can avail themselves of this service...even if they are not using DME. You just have to be flying home on one of the participating airlines.
HOpe this helps a bit.