Are they providers, non-pros, mixed bag - any clues how to tell the difference

It is a "mixed bag" and not worth the price of the middle-man. Delete it from your browser and and stick to what you found here.

They are a total waste of time and money.  The ratio of men to women is easily 1000 to 1.

I've been on AFF for over a year, and I've had an awesome time with it. But, there is a learning curve to learn. First of all, the people running the site suck!!. Their service sucks, and the site can be slow at times. It is, unfortunately, filled with many fakes and flakes. The fakes are out to get your email address, and the flakes just want your pics, without any intention of meeting. However, if you stick with it you will learn how to tell between the two. What I like most about it, is the fact that it's no strings attached sex, and that's all up front. But again, if you stick with it, it will work for you. Currently, I'm playing with 3 couples, and 3 singles, on a regular basis....

Interestingly enough I was a member of AFF a few years ago. I responded to an ad by a guy/couple who was looking for a guy that would bang his wife. I was happy to oblige on more than one occasion. But yes, the site is mostly BS.