I personally will never-ever use them again.
We waited almost 45 minutes-1 hour for a shuttle from the airport (they are supposed to run continously, and trust me, it isn't a 30 minute drive to the rental counter - I'd say it's maybe 5-8 min away depending on traffic). Many of us waiting attempted to contact the Rental Center to let them know that no shuttle had been by - the phone would ring, and ring, and ring until finally an employee picked up only to say the shuttle was "on its way".
Once we arrived at the center, there was one person working the desk to wait on us all.
We then got our rental car - it was moderate at best - gum stuck to the mats, stains, and scratches all over the car. At least it ran well!
Then we go to return the car - they print out a receipt and we get onto the shuttle to go back to the airport. While looking at the receipt (yes, we should have looked at it more closely before boarding the shuttle - our fault), we discover that they charged us the gas refill price when we declined it at the start and had brought the tank back completely full. Once again, tried to call the rental office, once again, they don't pick up (even the shuttle driver couldn't help us with getting ahold of anyone. lol)- so, we end up having to call the corporate office to complain - and then go through the hassle of faxing receipts to prove we bought gas etc...
Maybe I just had a weird string of bad luck?
So, did I get a great initial price? Yes. Was it worth it? No. Will I personally ever use them again? Heck no. LOL. That's my Advantage story.