Allowing different routes from a slide is great. Unlike conventional linear presentations this provides something closer to concept mapping. Arrange Slides allows you to view all your slides - if the view could be limited to the top level of a presentation (i.e. leave out all those accessed through down arrows) would allow you to return to the overview of a topic. Even better if you could use this view to jump around - going directly back to an earlier point quickly. These are two moves often essential in teaching (difficult in linear presentations). VUE (http://vue.tufts.edu/index.cfm) is an implementation of concept mapping but is less good at presenting and does not work only via a browser.