Rented most of the time in ROC, then LAX.

ROC
AVIS Preferred
Booked Full Size
Received Mid-Sized SUV
Exchanged - Prius

Couple of other cases:

AVIS Preferred
Booked Compact
Received Fiesta
Exchanged - Prius

AVIS Preferred
Booked Compact
Offered Malibu/Chrysler 200
Took: Chrysler 200. (Haven't tried that yet. Pretty good ride)

LAX
AVIS Preferred
Booked Full
Received Kia Optima
Too late to pick that up, so went back and asked.
Offered mid-size SUV
Exchanged: Camry SE

I know them pretty well that they don't mind giving me full sizes even after I book Compact. Just got AVIS First a couple of days ago, so we will see what happens with the upgrades. Wish it could be upgraded all the way to Premium. Anybody got upgraded to BMW from Full size as AVIS First?