One of the great things about zoom.it (and seadragon.com before it) is that if a user doesn't have Silverlight installed, the site will use Seadragon AJAX for the viewer instead with no big "Download Silverlight" button (although it is faster in Silverlight). 

Try the HTML5 Canvas version of Seadragon AJAX in the IE9 Beta, either by temporarily disabling Silverlight or by using the 64-bit version of IE (for which there is currently no 64-bit version of Silverlight).