Over the past thirty years, there have been a about a half dozen times when my bags didn't show up at the baggage claim in my arrival city. In each case, my bags were on a later flight. In each case, I either made arrangements with the airline's baggage office to deliver the delayed bags, or I returned to the airport to get them myself.
With Magical Express, that wouldn't be a problem. If a DME guest's bags are on a later flight, those bags will be delivered to the room later. The guest doesn't have to deal with the airline.
The second time I used Magical Express, our bags didn't arrive in our room until about 7 hours after we checked in. This may have been another case of our bags being on a later flight, or luggage delivery at OKW may simply have been backed up on that very busy day.
I remain a big fan of DME luggage delivery. The only people who complain about it seem to be the people who didn't read the part in the DME packets that explains that luggage is delivered around 3 hours after check-in. Those are the people who arrive in their winter clothes when it's 85 in Orlando, and who didn't bother to pack carry-ons.
Bring a carry-on with anything you'll need the first 12-24 hours. Don't bother to wait in your room for luggage delivery -- Disney pays the inbound tip so you don't have to be in your room.
Worry about the airline more than about Disney. Disney has a sophisticated luggage tracking system. In the unlikely event that your bag initially goes to the wrong hotel, it's not far way. But the airline could initially send your bags to Tokyo; that takes longer to fix.