Not sure about the advantage of this program.
I have been Select for as long as I can remember. I don't generally like upgrades. If I rent a compact car, I do so for gas mileage, ease of getting around in city etc. If I rent a full-size then I want comfort for distance travel etc. I guess the various upgrades from full-size to luxury are OK but not the same as upgrades from econo to business or first on airlines.
I would rather have a REALLY GOOD discount rate, along the lines of those available from our best discount code on this forum (Marshall School of Business or AVIS shareholders).