I'm of the opinion that when it comes to your kitchen knives, they should all be at their sharpest!
A dull knife makes for hard work.
I was trying to saw through a tomato until my husband, who is the ultimate knife sharpener, remedied that situation, tout de suite. One pass and like magic, I was through that tomato faster than you could sing "...you say tomato and I say tomahto..."
Sharp knives not only make it easier to do your slicing, dicing and chopping, but they can also prevent accidents. Yes, this may seem counter-intuitive, but there's a greater risk of slipping and slicing or stabbing yourself when you saw back and forth with a dull knife.
I like to put machines to work for me, as in Food. Processed., but there are times when they just won't cut it!