I find SB easy to use and if you're going to make a purchase or do a trial anyway, you might as well get compensated. I'm a long-term user and have made a fair amount of money from it.
Can't complain about the cashback, but literally every time I try to log in, I get an error message, even if I've just reset my password. Good money, but frustrating process.
I actually had an awesome experience -- I ordered two pairs of shoes on sale for my daughter. One fit; one didn't. I emailed to ask about the return policy and customer service replied, "We credited your account for the purchase price. You don't have return the shoes. We suggest you donate them to a charity."