I was skeptical about using ME, because I'm so used to the convenience of having our own towncar to whisk us to/from WDW. But I am soooo glad we tried it last time, because we loved it!!
It was easy to use, and everyone at our resort (ASMu) seemed well-informed when we had questions about our return trip. We were able to call only the night before our return flight and schedule an ME pickup...which we hadn't done yet only because we hadn't been sure when we were leaving!
The only thing I think they could improve on is signs/directions to the ME terminal in the airport.
Once you know where it is you should be fine, but the first time around can be confusing!