It all depends, as Rusty states. I have had great trips where we got on the bus, and took off right away. I have had trips where we waited in line for a bus, then waited some more on the bus. And once on the bus ended up being the last stop out of many.
The ride itself is around 40 minutes, but that doesn't take into account any waiting at the airport or on the bus, or the fact that your resort may not be the first one you stop at. My worst experience with DME was late at night, and it was almost 2 hours from getting on the bus to standing at the resort check in counter.