I think you should specify what type of critique you are looking for. The hacker news community might not represent who your early adopters are (Do we play sports?). In that sense, we might not be able to critique the market validity of your startup. And, we may not be interested in "critiquing" your new startup.

On the other hand, if you specified that you are looking for a critique on your site's design, usability, etc. then I am sure you could get feedback.

That being said, I responded with this insight because I fit into both categories (I design products for mobile and I played baseball at a D1 school).