I'm glad I found this thread, I've wanted to share our experience. We were at WDW from Oct 21st to Oct 30th.
At the arrival we were at the hotel less than an hour after we landed, pretty smooth process. We flew Guatemala-Miami-Orlando with American Airlines. When we did check in at the airport in Guatemala they hide the ME tags with the airline tags "because the scanners get confused"

even with the tags hidden, the ME people got them! We had to gate check in a third bag at Miami airport, we had put the ME tag but the airline people removed it later!!!!! we didn't get it at the resort with the others... (how could they know if it didn't have a tag!!!!) but they were great, they asked us for a description of the bag and what we had in the bag, the more specific the best. We got it the next morning before we left for the park.
The return trip was a nightmare from the begining. Our flight was scheduled at 10am, the bus at 7:15... it got there at 7:45 we did 4 more stops at ASMu, ***, Pop and another one that I don't remember.... got at the airport at 9am, HAD TO HAVE check in at the airport because it was an international flight.... a lot of people in line and we checked in at 9:30 when the flight was already boarding.... it was very stressful. In all the hassle because we were so late we didn't notice that a bag (the same bag that we didn't get at the arrival) was missing.... my husband ran to the ME counter, filled out a baggage claim but we were very pessimistic. We hadn't put a name tag yet.... (I know I know.... had I never taken a flight before???? don't I know to put ids on the bags???? well... yes I knew but we were running like crazy people and just forgot!).
Well.... we were the last ones to board and when we arrived in Guatemala (after so many other delays....) ANOTHER bag was missing, this time it was the airline.... filled another claim.
We called ME when we got home and they already had the bag and wanted to mail it. Since it would be an international mailing that wasn't practical at all so they told me they were checking with American Airlines if it was possible to send the bag with them. Next morning we got a call from ME informing us that the bag would arrive that afternoon (same flights we took the day before) and it did.... We also got the other bag... so it all had a happy ending
Overall ***** 5 stars for baggage handling and arrival trip, * 1 star for the return trip... too late, too stressful and too slow! however, I would certainly use the service again and just would make sure they know we cannot check in at the resort because it is international destination so they can plan to pick us up earlier or something like that.