I would ask people to spend 2 minutes with the website/product and then answer: 1) To what extent you understand what this product is? (scale 1-7) 2) To what extent do you understand how you could use the product? (scale 1-7) 3.1) How probable is it that you will start using the product? (scale 1-7) 3.2) Please explain why/why not? (open ended).

Having people understanding what the product is and does and how and why they should use it is the first gate you need to pass.