http://en.wikipedia.org/wiki/Polynesian_navigation

Why use any instruments?

By the way, what anchors did the Polynesian's use or how did they pick-up a mooring? ;^)))

Really folks, I respect the sense of sailing with minimal instuments except one's senses and some tell-tails. (Or is it tell tales?). However, the question was: What you think" The concept of essentiality is obviously relative.

If you're sailing in the fog where you can hardly sea the masthead, then your windex won't do much good. If it raining "cats and dogs", you'll not enjoy looking up at that little arrow on the top of your stick very sucessfully; and, the tell tails might not like beein really "sogged-up" in light to moderate winds. If you're running at night on a deep, deep, reach, then you really don't want to be looking up a lot while fight a mixed seaway, do you?

Essential? Not USUALLY in an absolute sense. But relatively, a number of us think such instruments are very useful.

Would we turn-back if we didn't have them working? Probably not, in most cases. But, then I like my 65# CQR on 250' of 3/8" HT chain in front of 50' of 7/8" three-strand nylon rode -- I don't think the "recommend" 85# Rocna or Manson is necessary. ;^)))) (Besides, my sprit pole would be jammed by those "new fangled", monsters.)