I'm sure these must have been raised before (I couldn't find anything though). Both these bugs are visible in the 0.92 demo.
The first problem is that you can drag a docked splitters beyond their limits leaving the UI in a dodgy state.
The second problem is exhibited when you resize the whole frame to the left. The centre pane gets completely hidden by the left hand pane. Instead the left hand pane should size down when the centre pane gets small.
I'd say that these are really critical bugs for a docking system....