The site looks really clean and nice to me, however:
You said your site is "XHTML and CSS valid". That may be, but there's no doctype, so it won't validate. It doesn't matter how well you write the code if it's not going to be rendered according to the rules you're following.
You can check your site here:
The W3C Markup Validation Service
Visually, it's very nice. I would personally change the footer links to they only have underlines on :hover or not, but not both. IMO, links should look like links. Yes, they have the traditional blue link color, but my preference would be to make them look and act like links - set them apart as such. But again, just my opinion.
As far as the CSS, that totally validates as CSS 2.1. There's not a whole lot there, but I would take anything you have inline and separate it out to an external file. Why make the search engines read through that?
Good luck with your site! I hope you've resolved any IE6 issues, at least until we can all say goodbye to that difficult browser!