My upgrade stats are similar to what IAHtraveler posted. Previously, when I was a Pres Preferred my upgrades were very sparse and nothing to write home about, so the move up in status a few years ago has been significantly better.
I also echo the comments about the Caddy XTS. The majority of the time, that is what is waiting for me in my spot. More times than not I will go up to the counter to switch into pretty much anything else.
I am also Hertz Plat but do not use them nearly as much as their prices always seem quite a bit higher than Avis.