I have one which I bought for aerobatics, where all the zippable pockets are very handy. I often wear it for other flights, just because it's so handy. Wearing light-coloured summer clothes for flying, you can be just about sure to end up with grease stains somewhere. WIth the flying suit, who cares. I feel a bit awkward going to the supermarket on the way home, but I've kind of got over that. As Genghis says, you cxan always take a change of clothes if you're going to work or meeting people afterwards.
I got mine from flyingsuits.com.