I think this would be very nice in an ebook or other long form writing where I need to backtrack to find some earlier reference. Where it doesn't work well is in hierarchical data like HN comments. I installed the chrome extension and used it to read the comments on this posting and it was nearly impossible to use. With things that are arranged hierarchically, such as comments, a single page works better than this, but I do think this will be nice on longer articles or with ebooks.