I have just had a look at that site and it is very professional, but also very calculating. I think the people who have set up the site have basically sold the big cosmetic companies on the idea that they can trial their products for them at a very reasonable price. It currently costs about £9 per person plus the cost of the product to get members of the public to try a product out for you. This website will be cheaper because they are only using sample sizes and the users themselves are paying a pound per sample towards the cost.
Its a nice business idea but I wouldn't mind betting that people who use it as consumers will find themselves being guided towards the products the big companies want to sell rather than ones that are suited towards their individual preferences.
Still, a pound isn't much money and you might get something really nice.