We rented from Dollar during the first week of October & did join their express club. We arrived around 10pm or so and, after collecting the bags, went right over to Dollar. Got in their express line, had everything all done (from waiting in line til on the way to the car) in about 4 1/2 minutes. The paperwork was all filled out, all the options were already selected (gas, CDW, etc). Just a quick swipe of the credit card (I think, not even sure they had to do that), a signature, & away we went. It does speed things up some, and sped up the return somewhat too.
Is it for everybody? No, some people don't want their information in the system like that, but, do remember, one way or another, they'll have the information in the system, whether it's before you arrive or when you get there. Either way, they'll have what they need before you get what you need.
Enjoy the Magic, & good luck!