I'm currently in a group and was also in one about 3 years ago. Both were time limited (10 sessions). The first group I didn't find helpful but I think that was partly because the leaders didn't choose the most compatible group. The one I'm in now is for sexual abuse and assault survivors...it's tighter knit and smaller in general. With the topic of the group, I'm having a hard time with how quickly we're having to move through stuff. But I like everyone and even though it's triggering, it's also helpful.
Both groups were free.. The first one was when I was in college so it was through the counseling center there. The one I'm in now is through the local women's shelter. So it's neat to have this kind of thing available for free, although that may not be the case everywhere.