Right, prepare for brutal honesty.
my first impression was that the site looks cheap, the logo is pretty poor imo (it seems out of focus) and the bubbles make the site look very dated.
I know you have the bullet points at the top, but in the first 10 seconds I cant really figure out what the site is about. Also, now that I do know, its tricky to find where i sign up, make that more obvious as users are your currency.
Id look at improving the site layout a bit, it looks like Drupal, and if so you should be able to make a really nice looking, easy to navigte site
As a final point, there is no indication of whether the site is live or not? ie no content that immediately makes me think the site is buzzing and im missing out by not joining. How many members are there, latest discussions etc. id consider this as people will only join things that are moving in my experiance.
hth