I did group therapy for about a month every weekday morning at an outpatient facility. There were maybe 10 - 15 of us in a room, led by a counselor.
Basically we talked about what our day was like yesterday (since we started at 9am). It was pretty structured - everyone got a turn for about 15 minutes each, and we had to stick to a certain format. We had to list our short term goals, what we did that we felt was constructive, what we had been feeling etc. At the end of each person's turn, others could ask them questions if they wanted.
As such it wasn't a terrible experience but it was a bit surreal sitting there with people you don't really know and trying to get support. Although I suppose that's not too unlike a forum environment like this.
And while it kind of felt good to talk sometimes, it wasn't all great. Like there was usually some dipshit who took up other people's time with their own problems, or else would have a strategically timed breakdown in order to get maximum attention. It felt a bit infantile in that respect.