I haven't had bad experiences with exchanges either, except ones that were my own fault (wasn't mindful enough and hit someone's DNW, ouch), and the occasional whingey feeling when my fic didn't get as much attention as I wanted (which happens with fics outside exchanges too). I mean, yes, I've had recipients who didn't comment, and that's annoying. But I write for my own pleasure as well as to please the recipient, so if they don't comment, I'm still glad I wrote something. Also, I'm in awe of how much work has gone into making exchanges what they are, and all the effort people put out to run them and to make sure everyone has a gift (pinch hitters, man!). They make me feel hopeful about humanity, overall.