I've been a full-time affiliate marketer for over 10 years and am so confused at the number of negative reviews. They were one of the first networks I joined and one that I am most active with still today.
Unfortunately I think people who have bad experiences in affiliate marketing in general always blame the network that they joined rather than the mistakes that they made.
I've been both a merchant and an affiliate on ShareASale and have found them to be one of the most transparent, honest networks in the industry. I seek them out at every conference to see what is new. I follow their blog for advice. I attend some of their webinars. They make every effort to try to educate their partners and work for the good of the ENTIRE industry (like being an Industry Champion of the Performance Marketing Association).
If you want to know if ShareASale really works, ask one of us who have worked with them for many years successfully because it's not a "secret." You read the guidelines, you ask for help when you need it, and you proactively manage your account using the data and tools in their system.