I can report that the free weekend is more hastle than its worth.
I recently gave it a try and when I arrived at melb airport to pick up the car, the staff told me that they'd never even heard of the Europcar loyalty program and were surprised when I pointed them to teh details on the web site. Next, when they looked harder at the reservation they found that there was some sort of coupon code on the booking, but the computer system wouldn't accept it, but told me that they'd investigate. Because I didn't want to pay for the risk reduction (I have separate travel insurance to cover the excess), I had to give them my credit card to cover tolls and any damage to the vehicle.
A few days after the rental, the full charge was charged to my credit card, and the rental was charged at teh full rack rate, not even the price I would have got if I'd not tried to use the free weekend. I have now been fighting for neally two weeks to get a refund. Spoke to their customer relations again this morning, to give them one last chance to fix things up before I lodge a chargeback with my bank.
Europcar does offer competitive rates, but my experience is that the free weekend offer is just a gimic and more hastle than its worth.
Like others, I have had a number of Europcar rentals and never had an upgrade despite that being one of the supposed benefits of Privilege Elite.
I'm still Velocity Gold, so might switch across to Hertz and see how their service and pricing compares.