Challenge modesFollow

Has anyone here tried them out yet? I only got started with a few guildies in the last days and I think they are immensely fun. They really remind me of BC HCs in terms of difficulty. The difference being that you operate under pressure because you want to be as fast as possible. I only got 2 bronze and one silver medal yet but I'm looking forward to completing the other dungeons and then start working on improving my finishing times.