You get what you pay for. There are going to be issues, but that's what you get for free. If you want flawless (which isn't ever guaranteed) you are going to need to pay for a town car or rental car.
DME is my least favorite means of travel because everything is out of my control, however, we will use it in August as it is just DS (6) and I traveling and we are in no hurry to get anywhere.
And the funny thing??? I have had more issues with car services than I have had with DME!! I have had to go in search of drivers, both at MCO and my resort. I have had drivers tell me no grocery stop will happen, even though one was promised.
I have always had good service with DME. Is it the fastest mode of transportation to WDW? Nope. But, having said that, here are my average times with various modes of transport..
DME...between 55 and 85 mins, most in the 70 min area.
Car service..carryon bag only.....45 mins.
Car service...checked luggage.....60 mins.
Mears shuttle.....to Dolphin, carryon only....85 mins.
I have never had an issue with my bags not getting to me in a timely fashion..well, there was that one time at POP, but that was a Pop issue, not DME. So, as you can see...a car service, with baggage, takes just a little less time than the average DME run.
So, for me, time really isn't an issue.
Issues with luggage??? IF it's upon arrival, and the bags are late?? It's one of two things...the airline misdirected it, or the resort was slow in delivering it. There is seldom an issue of DME luggage handlers sending bags to the wrong place. And if/when that happens?? Takes a very short time to realize the mistake.
For your departure back to MCO?? it's the RAC system that is taking care of the bags if you check them at your resort. There have been one or two cases of bags not making it to the plane ontime, but that just doesn't happen often.
And yes, a lot of guests feel that 3 hrs prior to flight departure time is excessive..but in all reality? Not really. You have an addtl 30 mins at the airport to worry about if using DME.