I only did one group performance and it was very nice. None of us was extremely nervous, only a little so we had to laugh at almost anything before going on stage.
During the performance I felt rather good. I only had the idea my smile looked very fake and I felt my lips tremble, but that got less and less during performing. I couldn't see the audience because of the lighting, so I had to smile towards a big black space
I never did a solo yet, but I guess I would be far more nervous when I had to do a solo.