Workflows can get big pretty quickly.
VS 2010 required scrolling vertically and horizontally to navigate larger, more complex workflows.
VS 2011 brings panning which is a much more natural way to navigate.
2010: No Pan
2011: Pan, yay.
Learn more about the designer improvements in WF 4.5 here: http://msdn.microsoft.com/en-us/library/hh305677(VS.110).aspx