100% safe. maybe you are worry that you give them provate key for trading thats why you are asking is it safe or not.don’t worry guys. etherdelta is 100% safe. after finished trade clean cache.
Yeah it's safe and if you're doubting just click the forget account in upper right corner every time you're done in trading. I always use ED and it's working smoothly with me.
But now since ED transactions are too congested because of this cryptokittens, try to use other exchanges for a while.