Changes from 6.0.x to 6.5
IntelliJ IDEA Coverage data
Coverage data produced by IntelliJ IDEA coverage engine bundled with TeamCity 6.5 can only be loaded in IntelliJ IDEA 10.5+. Due to coverage data format changes older versions of IntelliJ IDEA won't be able to load coverage from the server.
IntelliJ IDEA 8 is not supported
Plugin for IntelliJ IDEA no longer supports IntelliJ IDEA 8.
Unsupported MySQL versions
Due to bugs in MySQL TeamCity no longer supports MySQL versions in range 5.1 - 5.1.48. TeamCity won't start with appropriate message if unsupported MySQL version is detected.
Finish build properties are displayed
Finished builds now display all their properties used in the build on "Parameters" tab. This can potentially expose names and values of parameters from other builds (those that the given build uses as artifact or snapshot dependency). Please make sure this is acceptable in your environment. You can also manage users who see the tab with "View build runtime parameters and data" permissions which is assigned "Project Developers" role by default.