Definitely sweet enough for me now, but might not have been a year ago. I always liked dark chocolate, but typically 55% to 70%.
Then when I (or more accurately my wife) discovered the benefits of a low/zero fructose diet about a year ago, we cut out as much sugar from our diets as possible and found that our palates evolved quite a bit. Now I find 55% chocolate too sweet and I can't bear really sweet things. The book really is a life changer, but only for people who want to change their life.
I've tried a few high cocoa content chocolate bars, the Green & Black's 85% is fantastic, really creamy and, to me at least, not at all bitter. The Lindt 85% is a bit more bitter and not creamy, but tempers better than the G&B, so I use G&B for fillings and Lindt for coating chocolates, when I want a thick tempered coating.
Incidentally, I'm now 91kg, down from 107kg about 2 years ago. I went from 107kg to about 100kg just by cutting out random sweet things and eating very high quality chocolate as a snack (Amedei, Mast Brothers, etc). So without knowing it I'd already started to reduce my fructose intake. Then I read David Gillespie's book and cut out all the dried fruit and other hidden fructose and other sugars, which helped me get down to 91kg.
Not sure how much more I can lose, given that I'm 6'4", but we'll see...