Always worth asking, but we've had very mixed results. A few trips, we were able to cut down long waits to walk ups. One time, we were quoted something like 45 minutes at Mythos. When we showed our room key, it dropped to 5 minutes.
The last few trips, though, it's been useless. Many places said they only start using the Priority Seating when the wait is greater than an hour - of course, we ran into mostly 45 minute waits (week before Christmas), so we couldn't use it. They said if the wait was an hour or more, the Priority would drop the wait by 50%.
Last Christmas, Toothsome was doing Priority and said the same thing. But when the wait was 90 minutes, we showed our key and they dropped it... to 85 minutes. I believe we ended up at Vivo that night where the wait was less than an hour, so we had the full wait.