My first impression is that the design is NOT clean. Clean, to me, can entail a large amount of content organized in a neat and easy-to-read way. Your design is simple, which is good, but a bit cluttered. My suggestions to you:

1. There are two lines that comprise the category links in the header and the two lines are arbitrarily aligned. They're off-center and don't look good adjacent to one another.

2. The thin scrollbars are cute, but they're a usability hassle; make them thicker so I don't have to pinpoint my clicks.

3. The logo is simple, which I like. I would suggest making it slightly thicker or somehow more prominent.

I second Kyro's second and third points. I thought perhaps these problems were due to Chrome, but the site looks identical to me in FF3.

Check out popurls and alltop for a super-clean design for a similar aggregator. Keep up the good work!