SeashoreCM is right...just happened to me yesterday. OK...didn't cut it TOO close, but close enough to stress a bit.
Plane departure was at 6:05 pm. ME pickup was at 3:25. We were waiting at the CR lobby by 3 pm, then walked outside to get on the bus at 3:15. We had checked our luggage earlier, so at least we didn't have to worry about checking bags and getting boarding passes at the airport. We left CR on time with a few families at 3:25. Went to GF and picked up a few. Went to WL and picked up a few. Then doubled back to Poly and picked up. Took almost an hour to get off of WDW property!
Got to the airport at 4:50 pm. Line for security was super long...thankfully, it moved way faster than it looked! I had even gone back by the Continental ticket desk while my friend was in the security line to let them know we were here and trying to get to the gate...one of their reps named Tom was a total jerk and berated me that I should have gotten to the airport in time to get through security. Well, who would think that a pickup time of over 2.5 hours isn't enough? Good thing it turned out that the security check was faster than the line made it appear to me, or DME might have heard from me. I really think the worst issue was how long it took to pick up the other guests on our way out. We made it through security in PLENTY of time. Also think that the Continental rep could have been a bit more positive and told me that to hang in there, that the line looks bad when it, in fact, is moving at a good rate.
I also didn't like the long line for check-in when we arrived at MCO. Seems like we could have gone straight to the bus lines since we had our vouchers in hand. Don't think I'll use ME on the next trip.