Users can now see who visited your site. When you are on your own blog...click on the number of visitors that have gone to your site (for example: 14,500 visits), and you will be taken to a page that shows who has visited your blog (and when). There is also a link to this page from within your admin area. Only YOU will be able see this information.
Note: If a user has selected to to browse anonymously, you will not see them in your list. (though that is no fun!)