This week's book giveaways are in the Refactoring and Agile forums. We're giving away four copies each of Re-engineering Legacy Software and Docker in Action and have the authors on-line! See this thread and this one for details.
While for the most part Struts 1.3.x is backward compatible with earlier versions, because of the new composable request processor, if you're using Tiles, you must make some configuration changes in order for your application to work with Struts 1.3.x.
You must add the following initialization parameter to the Struts ActionServlet in your web.xml file. The chain-config.xml file that it points to is in the struts-tiles-1.3.x.jar file.
Also, don't forget to update the DOCTYPE definition in your tiles-defs.xml file: