Looks good, I'll agree with what was previously said. Also, a few minor things -
*The arrow buttons on the preview tabs could be less transparent, and have the arrow centered a bit more inside the square
*The logo could be anti-aliased
*You use a right-sided drop shadow for part of the header, but nowhere else on the page. The use of grey gradients looks very professional, but incorporating a drop shadow to the other areas of content on the page would help (it looks somewhat flat, currently).
Otherwise, very nice!