Location: SAN
Class Reserved: Premium Group G
Class Received: "Special" ... got a Volvo S60 with 12 miles on it! It was excellent.
My Status: Pref Select

Location: N3H (Calgary, AB off airport, local)
Class Reserved: Intermediate Group C
Class Received: SUV: a new Red Jeep grand cherokee w/ 2,000km on it. Again, excellent.
My status: Pref Select

I certainly don't walk up to Avis expecting any of these upgrades - it's nice to have them once in a while, but if I have to drive my Sebring or Malibu (which is what I'm paying for!!), that's OK with me - it's just a car. No big deal.