What Happened in Essen
At the time of creating the branch, KOffice was still developed in KDE's Subversion, which means that it was difficult to manage branches. Very difficult. But we still felt it worthy to create a feature branch when KOffice trunk got frozen in preparation for the KOffice 2.3 release.
This branch gave all developers the opportunity to share work they were doing on new features, share refactorings and keep track of each others work, while at the same time pulling together to make trunk as stable as possible for the release. When the branch was created there were some fears that everyone would move to the branch and nobody would fix bugs and work on making trunk release ready, but those fears have been proven unfounded, just like the previous time we had a feature branch during release freeze.
Bug fixes always went into trunk – and trunk was regularly merged into the essen branch by Casper Boemann. So what went on in Essen specifically?
Optimization work on KWord was an important item - and these optimizations were quite dangerous in the shorter term, and really shouldn't be applied to a release branch. But they showed the way forward for the Calligra Words text layout re-engineering Words maintainer Casper Boemann has embarked upon.
Parts of the ODF specification that weren't supported previous were implemented by, among others, Sebastian Sauer, like ODF draw:auto-grow-width and draw:auto-grow-height.
Adam Celarek added a docker to Krita that provides an alternative way to select brush presets from the toolbar popup, following a wish by artist David Revoy.
Boudewijn Rempt (that's me!) worked on experimental caching for complex shapes. Currently, the text shape for instance always repaints the text in a paint event. This code caches the text shape as a QImage, and paints the QImage. It's still experimental! Marijn Kruisselbrink did the same for the KSpread canvas.
Adam Pigg started working on a mobile version of Kexi, after having received the donation of a Nokia N900.
And so on – while at the same time, bug fixing and stabilisation of trunk proceeded at a strong pace in order to prepare for the 2.3.0 release.
After the release, Ian Monroe, sponsored by KO GmbH, finished the conversion of the KOffice svn repository to git, making Essen the new master branch from which the Calligra project is working now. (Ian, by the way, is also working on the kdelibs and kdebase Git conversion, which is expected to be finalized any time now, also sponsored by KO.) KOffice 2.3.1, with many fixes provided by the Calligra team, will have been released by the time you read this!
In the future, Calligra won't need feature branches during release freezes - with Git, branching is so cheap that only finished features will be merged into master, meaning that master is always ready for release!