I have read that with more pixels comes the need for better technique to get sharp images. The only problem with that is he was on a tripod so his technique should be perfect.
I have both a D90 and D7000 and I don't really think I see a difference in sharpness. The D700 that reviewer has is amazing and much sharper than the D90 or D7000 can ever hope to be. It would be nice if he would take the same photos with his D90. Maybe he'd realize it's about the same as the D7000.
I have some comparison photos here: http://www.flickr.com/photos/traceyandkevin/ You will need a Flickr account to view the original files.