Well hey, after co-moaning with +Guy Stalnaker about +GIMP's new insistence that I must save the intermediate stages of any "Image Manipulation" I do in their proprietary format, I have found that +Akkana Peck came to the rescue a while back when I wasn't looking.
Now as soon as I can bind this to Ctrl+S I'll be happy again. Mind you I do still wish these people could live with the kind of "by clicking save you acknowledge that you aren't saving everything about your image manipulation session" kind of approach that Libre Office and other apps that deal with multiple formats use...