I love the Smart Options Display - I have it mapped to the "1" key and use it often.
I have it set to tool options, previous tools, views and snapping.
I always use 'tool options'
I love using 'snapping' to quickly suspend and reset snapping.
I never use 'views' because the number keys are too convenient - but could see this being helpful on a macbook...
but 'previous tools' is almost useless as the definition of 'tool' is so limited.
One