Users can define their own measures, for example the burned budget or the team size. This feature was already there prior to version 2.10 but has been heavily refactored in order to support all adjacent features like time machine, variations through time, filters and treemaps. Unfortunately existing past values can not be kept in the new system, so only the last values will be available in version 2.10. Moreover projects need to be analyzed after the migration, as it's recommended in upgrade guide anyway.
The properties sonar.java.source and sonar.java.target define which Java version is used to compile sources. The default value was 1.4 and has been increased to 1.5.
It means that analysis of Java 1.4 projects will probably fail if these properties are not explicitly defined.
Previous versions of the Views plugin are not compatible anymore. This plugin must be upgraded to version 1.5.5 :