When you reserve your ride with DME, you will be sent a luggage tag for each person on the reservation. If you need more than one tag (if you are checking more than one bag per person) you can call DME and they will send addtl tags for you. These yellow tags are bright lemon yellow..really hard to miss. They are about 18" long, so when you fold them over the luggage handle, there is about 9'' of tag now...with black lettering on it. It's really hard to miss. When these bags come off the plane, they are put aside, right away. The luggage people who get your bags off the plane know what to look for..they are so used to seeing these tags they don't even think twice anymore..just grab that bag and put it in the DME area.
THen, DME workers come along, scan the bags. The bags are now distributed to the appropriate resort area...Epcot area, DTD area, MK area, AK area..etc. Then, they are scanned again, and put into resort specific areas, then put into cages for each resort and off to the resort they go.
I have used DME more times than I can remember. I have never had an issue with my bags. You stand a much greater chance of having the airlines misdirect a bag vs DME.
As already noted, pack anything you will need to start your WDW stay in a carryon bag. That way, if the airline misdirects a bag, or it's slow in arriving at the resort, you can just head out and start your fun vs hanging around at the resort, waiting for the bags to get there. That can take up to 4 hrs!!!
And the one time I didn't pack my carryon correctly??? That was the one time I really should have. Our flight had to go back to Florida (due to snow) and we had to spend the night in Fl. If we had packed our carryon bags correctly, we could have stayed in Philidelphia for the night!! Our bags wouldn't have gone with us, but they would have delivered them the next day, and we could have saved ourselves an addtl 6 hrs of flight time. We could have spent the night in Philly, and taken the first flight out the next day to Providence. But since the carryon bags weren't packed correctly, we had to return to Ft Lauderdale, spend the night and go back to the airport early the next morning, go through security again, and fly another 3 hrs to Providence!!!! Learned my lesson that night!!