The header looks great. I love the logo and use of colors. It starts off very rich with the blue search field and sign up button. Unfortunately it is downhill after that. Below the search just does not seem to match for me, plus like gaucho said it looks similar to many other pligg sites.
It can be saved, if you can use those rich colors on the bottom half like you did on the header it will give you something nice to look at. Make users want to come back.
And of course if you value my opinion please feel free to leave some rep
Snezo 
