@helge the only place I like them is for media files (audio, video, image) where you might want to serve back e.g. a smaller .webp file but only to browsers that support it
For APIs they drive me up the wall, because I'm often doing API research from devices (like my phone) that don't have a convenient terminal to hand
@simon I think it is useful to have resource variants that are also addressable by URL, like /calendar/x/1.ics vs /calendar/x/1.html or /calendar/x/1.json. But that you can have /calendar/x/1 and have that resource serving the proper thing via Accept, is an HTTP superpower to me.