Sitewide links are really very helpful... well the reason behind this being that it not only gives you links for various pages of your site that helps in increasing PR.. for eg. consider
www.v7n.com it has thousands and thousands of links from where... from this very forum and blogs..directories...etc... well PR is not that helpful for rankings but they look good.. and the second reason being they are giving you free "anchor text" links to your website...now i guess everybody knows tha power of anchor text links...
Take care