I have met two donor offspring
I met a donor daughter through DSR in 2008. She was just married, had known all her life that there was a sperm donor involved in her origins, was wondering about who that was. She had been able to track things back through her mother's clinic to the sperm bank which, through some mysterious clerical error, gave her copies of all the papers they had about me. So if we hadn't connected through DSR, she would have found me anyway. She lives 30 miles away. I've met her family, she has met my family, I've been at the hospital when her kids were born, have visited them often as the kids have grown, have gone on vacation with them, etc. It's worked out well for all, nothing has really been difficult about it. Knowing them has added a lot to my life and I like to think that I have added to their lives.
I later met through 23andme a son of close to the same age. He had done the test for health info available at the time and, incidentally, made himself visible to others on 23andme. He did not know about his genetic origins and had not been looking. He had some difficult conversations with his parents afterward. I don't know that his life is any better for knowing. I am glad to have met him and his wife and kids, I talk to him occasionally on the phone but they live far away and, trying to think practically, I don't expect much more to come of this for me or for him.