The advice and histories on this site helped me to put my M back together again; however, I have never told my H about this site. As a MLCer, his memories of his depressed years are rather hazy, and I don't think this site could offer him the same sort of support that I got from it. That said, the information I got here is crucial to how we've reworked our M. If H had another EA ... it wouldn't matter whether he'd found this site or not: once was enough for me.
In terms of others who've saved their marriages, there was a woman called Morgan, later SallyM, whose H found her writing here. He was furious, but kept reading and was amazed by how highly people regarded his wife (and criticized him). It forced him to work on himself, and they were reconciled. HOWEVER, she was pretty much unable to post here any longer, talking about specifics, because she knew he was looking over her shoulder, which lost her the support network she'd built up here.
On the other side of the coin was a lady called Rotzilla or something like that, who had her H come and do a thread together with her after she busted his affair years ago. She was back last year, now that her H was in MLC, and found that his knowledge of her DB tactics was used against her.