You will also need to update the style sheet to point to version 1.6:
<link rel="stylesheet" type="text/css" href="http://serverapi.arcgisonline.com/jsapi/arcgis/1.6/js/dojo/dijit/themes/tundra/tundra.css">
Here is a brief overview of the features added at version 1.6:
- Support for Dojo 1.4.1
- Ability to rename Dojo namespaces
- Support for the Web Mercator Auxiliary Sphere (102100) as an overlay spatial reference for caches created in the Google Maps/Bing Maps tiling scheme. You can alternatively continue to use Web Mercator (102113) as an overlay spatial reference.
- Several bug fixes
For a complete list of enhancements and bug fixes, view the ‘What’s new in Version 1.6′ document.