I've had good and bad experiences. As far as good, I saw a post where a kid was sad no one would play trials with him just because he hadn't beat it. I didn't realize his age, but I agreed with him and sent him a request. My friend and I were just doing normal Crucible when he joined. He sounded younger than anyone I'd ever played with (not even typical 12 year old, but like 9). He was slightly energetic and would get on a less tolerant person's nerve, but he was nice enough. We got chewed up and spit out in Trials, but it wasn't the blame game that normally results. He was just cool with it. It was some of the most fun I've had with Trials.