Just read an article comparing the Macbook Air and two Windows machines and the Air was the clear winner as far as what computer the testers would buy with more than half the testers Windows-only users. Here's the article:
http://computerworld.com/action/article.do?command=viewArticleBasic&articleId=9103658&pageNumber=1

http://computerworld.com/action/article.do?command=viewArticleBasic&articleId=9103658&pageNumber=1