Mountain Lion has added the ability to view multi-page previews of Word documents when you hover your cursor over the icon, as has been possible with PDFs since Lion.

To see a preview, hover your cursor over a Word document. You’ll see two arrow icons on the document icon; you can click to the right or left to view different pages.

However, in Icon View, these previews only display if the icons are 64 pixels or larger. They display in Column View, and in Cover Flow View, no matter what size the icons are in the top of the Cover Flow View window.