Tapestry 5.6.2 is a drop-in replacement for Tapestry 5.4, 5.5 and 5.6 releases. It's a recommended upgrade for 5.6.1 and 5.6.0. To upgrade, just update the dependency in your build configuration (Maven POM, Gradle build script, etc.) – or Download the new JAR file -- and the new version will just work. However, please review the How to Upgrade instructions before upgrading.
The most interesting improvement is TAP5-2640 - tapestry-json improvements (implement Collection/Map, better exceptions) CLOSED : better exceptions in tapestry-json code, plus JSONArray now implementing Collection and JSONObject implementing Map.
Please check all the details in Release Notes 5.6.2.