I kid you not, the quote below is taken directly from their site as instructions for site testers:
"Be as critical as possible when reviewing a website. It's ok to be positive but don't just talk about how great you think their site is. These websites sign up for BetaPunch because they know they have things that can be improved upon. They want you to be as honest as possible with them as to your feelings about their website. Figure out what makes sense to you and what doesn't. And be sure to VOICE your opinions as you navigate the site."