I'm not privy to actual working conditions at Amazon, but the Economist made this chart that chronicles the growth of Amazon in the past 20 years and it lends credibility to the idea that the work conditions must have been relentless in order to achieve such massive growth. The article has been criticized for lacking sufficient data, relying mostly on personal anecdotes of former employees. It's difficult to ascertain the truth, but as the saying goes, " where there's smoke, there's fire."
Jeff Bezos, the CEO of Amazon, said that he didn't "recognize this Amazon."
The good thing that can come out of this is that the working conditions at Amazon will improve and customers will realize that there is a hidden "price" for the cheap prices that Amazon is able to offer (namely that it deprives workers of additional benefits).