For some of the garden I blow the leaves into a corner where they can mulch and in more formal parts of the garden I Hoover them up to place in the mulching corner or compost heap.
None really. They have use in clearing pavements, if the operator gets the leaves far enough away so they don't drift back soon after.
But you never see one used in Kew Gardens or RHS Wisley gardens, and there they have proper professional gardeners, and apprentices. They leave the leaves on the lawns and let them blow about or settle and be dragged down by worms. In the event that they would compost them, they'd simply rake some up in a heap and carry them off.
As a "proper and profesional" gardener, i use a leaf blower all the time to blow leaves from the paths and even off the grass. I do look after a garden that is open to the public so maintaining the safety of the paths is paramount. It would also take me all day to sweep them whereas a blower take 2 hours.