OTO - I have attended many of their parties. I never joined in any way, though I went to a few feasts between 3 different groups in the US and abroad.
I was considering joining, but didnt because I'm hard to commit.
I understand the Christian perspective that OTO is satanic, on the surface they want to end christianity and move to the new age of Horus / Crowned and Conquering child.
Many, if not most of the friends I met in the OTO are SRA victims, I can understand their revulsion. Also the historical records back up their desire to start a new faith. Thats what Moses did, its what Jesus did, and the Thelemites say that its what Alister Crowley did (With Thelema, the official religion of OTO).