Manual line breaks (Shift-Enter) are handy when you don't want to go through the drama of changing the paragraph spacing to tighten up two lines.
They can also be used to add text under a bullet without creating a new bullet if you want to add second line but don't want to type all the way to the end of the line so it wraps. Text in a table cell, for example.
Almost as heretic as using the Enter key to force a line break, but it has it's uses.
