We've brought inflatable PFDs with us (flying from Newark to STT) on maybe 5 trips. Always in carry-on.

We've always gotten them through -- maybe we've just been lucky. I think one time we were questioned about them, and showed the screener the TSA policy (which I always bring along).

I unscrew the cartridge from the inflator, so it can't inflate accidentally, but leave the cartridge tucked into the PFD.

Dan