I read a post by Adam Lasnik from Google in the Google Webmaster Help Group on the supplemental index. He said that the way to bring pages out of the supplemental index into the main index is to "Get more quality backlinks. This is a key way that our algorithms will view your pages as more valuable to retain in our main index".

If you have thousands of product pages from your site in the supplemental index how in practice to you get them all "...more quality backlinks"?