Years ago, back before there was a DME, Mears was the only 'shuttle' service to WDW. YOu could rent a car or use a towncar service, but those options were costly. The problem with using Mears back then, was that the bus usually stopped at multiple stops, outside WDW, before getting to the WDW resorts. If you got lucky, as I did, you got put in a van, with others going to your resort. That was a pretty quick trip, but if you got on the full sized bus, you faced a possible 2 hr ride, around Orlando, before getting to your WDW resort.
Then, DME came along. Yes, Disne contracts this service out to Mears. Disney makes the rules and tells Mears how the service is to run. But, Mears drivers drive you on Mears buses....with that Disneyfied look. And it is much better than the old Mears service.
Now...with that being said, and understanding how much I didn't care for my one and only true Mears experience, I had to get to the Swan a few years ago. I decided to use Mears, rather than spend the money (more than double) for a car service. I booked it in advance, got to MCO and printed out my ticket. I walked out to the bus area, was given a call beeper thingie. About 5 mins after I sat down, my beeper went off, and I was the last person put in a van....nicer than a bus. The vast majority of the people were going to non-Disney resorts. The driver was wonderful...he kept up a stream of jokes, and local information. Those of us riding in the van had a great time chatting with each other. It took about 15 mins longer to get to the Swan than it would have if I had taken DME...taking into account the waits at the DME counter, in line for the bus, on the bus, and then the subsequent ride to the resorts.
I had only carryon luggage so didn't have to stop at baggage claim first. I would do the Mears shuttle again if it were just me traveling. It was $19 for just myself, one way (I was moving to BCV for the last few days of my stay so could use DME going back). If it were more than two of us, I would most likely use the car service only because of the cost. A car service will be about $50 one way, Mears would be $40.