I don't know what everyone is complaining about. If your offer isn't credited, email them at *******@trialpay.com and they will credit your offer manually. Sometimes, like all affiliate systems, offers aren't successfully tracked.
That said, TrialPay is only the "payment" gateway of a site. If you don't receive the software/product you ordered, that is not TrialPay's fault (assuming the offer was credited as intended), but is instead the company's (whose product you are intending on getting for free) fault for not providing.
Just as if you paid by PayPal, TrialPay is not in charge of your product's delivery.
Remember, TrialPay's motto is: "try or buy something you want, to get something you need, for free". The thing you "want" is the TrialPay advertising offer you are completing. It's important to note that this may not be free. However, the free part is (contrary to most people's understanding) that you get the product you need (the software for example, that you didn't wish to pay for) for free, sort of as an incentive or "thank you" for completing the free OR PAID, TrialPay offer.
I have used this many times. It always ends up saving me money. If I need godaddy hosting, for example, I find a site that supports the TrialPay checkout to get some software for free, just for buying some Godaddy hosting (one of the TrialPay offers). If I want to unlock my phones, I go to http://www.freeunlocks.com (moderators, please remove the link if you wish. I'm just making some clarifications using genuine implementations of the TrialPay system), for example, which supports the TrialPay checkout, to get a free unlock code (to use the phone with any network worldwide).
Hope that clears things up... They are not a scam in any shape of form.