Probably just my age-related CRS, but I don't recall ever having read or heard before that I should NOT be using my inflatable PFD when it is really near or below freezing.  I need to swap out PFDs.  Just read this on Mustang's web site:

"This marking is because cold air below 0C and cold water near 0C can negatively affect the inflator’s ability to puncture the CO2 gas cylinder (both manual and automatic); thus, the device does not inflate.  If it does inflate, the time to achieve buoyancy can also be significantly delayed, and it is possible the device will not produce the full amount of required buoyancy.

Inflatable flotation devices are not recommended for use in temperatures below freezing.  As temperatures approach freezing, your inflatable flotation device will provide less buoyancy and will inflate more slowly. At temperatures near freezing, the device should be worn partially inflated to ensure that some buoyancy is immediately available to you if you fall overboard. The oral inflator can then be used to top up the flotation device after CO2 inflation. Cold reduces the volume of gas and results in a reduction in buoyancy."

I've been wearing mine through many below freezing trips. I will swap to my regular vest for the winter. It's warmer anyway.

Just as dangerous can be the clothes you have on.  Many ice fishermen have drown because their gear filled with water and weighed them down.  The old sourdough I fished with as a kid didn't like boots that tied.  If you can't kick off your boots then you're stuck in your bibs.  

Styrofoam is very warm, it’s like putting your torso in a coffee cup to go 

Once I started kayak fishing, I switched to a foam life vest. I'd rather sacrifice a little bit of comfort (although my NRS Chinook is really comfortable as far as foam vest go), in favor of being 100% sure that it would float me if I needed it. I've only ever needed it once, and it did it's job perfectly.