It enebles the GUI to have specific dock regions, where you can arrange document windows. Makes it way easier than using splitter controls inside a grid - they come for free then. The user can arrange the windows like he wants and even remove them from the position an put it on a different screen.
I think that gives an additional functionality and a good look too...
- AvalonDock gives an easy to use addition to handling in page windows.
- WPFToolkit used as chart library instread of WPF 4.0 buildin charts (Toolkit is a bit more advanced featurewiese).
- Another library to maintain and keep updated.