Got one recently, same time as my Vulture II. The PFII is a terrific small sack.
I've done a few walks with it so far, maybe 30 miles total over the hills, and I generally forget I'm wearing it.
It holds enough for a day, with a Guyot bottle in one side pocket and a flask of coffee in the other. I strap my coat on the top (and my wife's!) when it gets warm and it's still comfortable.
Seriously, it's a terrific sack.
As a bonus, it rides high enough (just, for me, I'm a shorty, better if you're taller) that you can have things on your belt below it or even wear a waist pack. I tried it with my Sabercat and it just fit.
The wide opening main compartment is really easy to use compared to the top-openers I'm more used to (alpine sacks) and the front pocket holds a few knives, maps and chocolate bars!