we booked one way- no prob, going down. I have read a few folks that had to leave the resort really early like between 4 and 6 am, and a few had probs, but apparently, when the ME bus failed, WDW provided a taxi and it worked out. Book away!
I just got back and was able to get ME back at the last minute. My ride had to leave early so I called ME from my room at Pop Century on Saturday afternoon and was able to get a trip out for Monday afternoon. I had to leave Pop at 1:45 p.m. for a 4:50 p.m. flight but considering it was an emergency I was pretty pleased.