The most valuable feedback is seeing of first time playing your game. And it can be easily broken by giving people same game second time. They already know details so experiment will be not clear.
What if create service that help indie and not indie developers to test games ( or apps ) and receiving feedback by recording screen, webcam and input of player. Each person have an account in such service and balance like money for example you can upload your game and receive 5 feedbacks, If you rich that limit you cannot receive feedback anymore.
You can restore your balance by playing other developers games or paying money. The most important is to record screen and input so such service can be build in Steam or Windows Live.
With such service you can test of first time playing many times instead of playtest group.