Have to agree with HOOK and DRP79 on this one.
I have a Mustang self inflating vest. I wear it 100% of the time on the boat, but never on the Vedder. As DRP said, if I'm facing a sketchy looking wade, I find another way around, or I just go fish somewhere else. 99% of the time I'm fishing on shore or in to my calves/knees if the water deems it necessary to wade out a bit. If the water is too fast or even remotely sketchy I don't wade out. IMO if you DO fall in and are wearing waders, your CO2 vest almost certainly does not have enough flotation to keep you above water, and without a crotch strap will likely get pulled right over your shoulders.
If wearing waders make sure you have a wear a wading belt! I like the strechy neoprene ones. They stay snug and are more comfortable than one with no strech.
Now, if I go shore fishing on the Fraser I DO wear my PFD. Generally I am wearing old runners and shorts. Also it seems the places I go everyone insists on wading out, so I have to as well unless I want to be snagging everyone in the legs everytime I reel in
So I wear the PFD as if I were to slip and fall it might give me a chance.
I do see the odd guy wearing a PFD on the Vedder, and it's usually someone wading WAY out to their waist, or crossing somewhere quite sketchy, or fishing on some rock upriver and one slip and it's gonners. My point is don't be fooled into thinking your PFD will save you especiallyif you have waders on. If you are wading and fishing safely, esp on the Vedder in the lower water months, you shouldn't need one.
Kind of reminds me of my youth and when I jacked up my truck, put big m/t tires on it, a winch, etc. The extra confidence offroad just got me into WAY more trouble, stuck beyond belief several times, etc. Now that I drive a stock 4Runner I never find myself in such situations, as if I need to go through someplace that looks too mucky, or I dont think I have the clearance, etc, I try to find another way or or I abort and go check out a different lake.