I have been using e-rewards since I was also sent there by gamestop. I figured, "why not?" Anyway, I have only received 2 GS gift cards. I don't lie because I don't want to ruin it for everyone else. Sometimes it's worth it, sometimes it's not. You will run into the occasional survey which asks you for 5-10 minutes of answering questions before telling you that you do not qualify (though we can all assume they keep those responses for their survey anyway).
Whether it's worth it or not will depend on what companies need survey's done and what demographics you fit into. Chances are, if you're a white male under 25 making under 20k a year without a college degree or fancy job, your survey selection will be more limited. If you are a minority female over 30 making $100k a year with a post-grad degree and you're a CEO of a company, you'll probably get requests for surveys every day. In all honesty, I get 5 or 6 requests per week, sometimes more, sometimes less. Most surveys are only a couple $s IF you qualify, but others can be as high as $15 or $20.
The one thing I do not like is the dollar system. It seems like the GS gift card is the only one that requires you earn $50 before you can trade for $25. To me though, I can do these surveys while I watch some TV or doing nothing, so it's worth it. Takes a while to get the gift card. I have also ordered magazines and a few other things, but the prize selection sucks. I'm hoping that they add to it as time goes on, like maybe some tangible items, but it's okay. Certainly adds up quicker than Club Bing.