First off, I held on to mine and would wear it (minus badges......) if I felt the need to (primarily if I felt there might be a fire risk). I certainly still wear the calf skin gloves all the time, as they are both practical and fire resistant.
On the very odd occasion that I have worn the old flying suit I've been the subject of a bit of critical comment, so I've decided to get one made up to the same pattern, in the same Proban material, as the ex-mil one, but in black instead of olive drab.
There's no doubt that a flying suit can be very practical, but I guess the real issue is one of style and image. I personally think that those who wear ex-mil kit when flying light civil A/C, complete with badges etc look complete t*ss*rs, but that's just my opinion. If I was going for a whizz in an old warbird, then I'd feel quite comfy wearing my old suit (although it is a little tight around the midriff now........). Climbing into a Cessna in the same attire somehow seems innappriate.