I used it a few years ago when I was looking to hook up with women with no strings attached and found that it was mostly couples. I actually ended up meeting2 different couples who were both great but 1 ended kind of weird after we got together, (she was wanting to have an affair with another man and felt guilty, so she wanted to even the score), the other I never spoke to again. It seems to be mostly men on that site and they harass like crazy. It's also really expensive.. something like 2.99 for every message you send someone i think.
Sort of a similar experience for me too. My ex GF had an account for us and she was looking for NSA female to play with us. We met an attractive woman at her place and had a fun evening together. She wanted to repeat and I was all for it.
Turned out her BF was unaware of her having a 3 some on the side. She left her computer unattended and he read all the messages etc.
He would message my GF several times trying to see her one on one; sort of a revenge fuck if you will.
My ex got fed up with the whole mess and terminated her account.
I got an account shortly after I broke up with her and met a few ladies. Some were fun but I wasn't the committing type so I moved on. Now I'm here trusting the care of my libido to professionals
So I guess from these trysts it was good but as Lisbeth mentioned, the costs are crazy expensive if you send 50 PM's etc.