Symfony 2.4 comes with a great form debugger panel in the Symfony Profiler. That was probably one of the most loved feature introduced in 2.4.
In Symfony 2.5, this form debugger panel UI gets even better with a collapsible form tree on the left and collapsible sections on the right; the browser even remembers which layers were collapsed or expanded after a refresh. The UI is also cleaner and easier to understand with interesting information expanded by default, and erroneous fields also highlighted.
Here is how it looks like now: