This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
Throughout the book there are statements in how something is not in a previous version and what is new in Tomcat 6. For the most part migration should be relatively easy as many configurations are nearly identical. However, there are a few changes to the configuration and the book does make clear note of that.