Over the last few years I've been playing with some older people (and not so old) who wear hearing aids. I haven't asked any of them (yet) what affect that has on their perception of their sound, or of other players' sounds but my grandfather who had one (over 20 years ago now) told me it was like listening on a telephone (which I imagined to be the 70's/80's quality version before the modern/improved compander electronics came in).
I rely on good feedback from my ears to know if I'm playing the way I want to (usually try to play warmer, richer) so I don't know that I'd play so well if I couldn't judge the quality well enough. Thinking back to what my grandfather said I wondered how trumpeters with hearing aids get on, and how well their hearing is restored using the aids. I know players both with and without hearing aids who have in my possibly untrustworthy opinion very poor tone quality (and they don't seem to be bothered by this), as well as a young lady who has an absolutely fabulous voice despite being almost totally deaf (and she wears two hearing aids) (and she sings, doesn't play).
Also, is this an insensitive/touchy topic to be talking about?