I did not like Nectar at all. Cacao was the best by far though. Some background:
I started with Coffeist when it first came out because I wasn't really ready to commit to a whole box of Original if I didn't like it. After that, I didn't order again for a while and by then Cacao was available so I gave it a try, along with a box of Original and Nectar.
For all the flavors, I've taken to adding some sugar syrup to sweeten to my liking. However, this trick didn't work for Nectar - it was not palatable to me either plain or sweetened with syrup.
I've also found that Cacao is much smoother than Original or Coffeist. For some reason. I get a hint of a fibrous or maybe sandy texture from the other 2, but Cacao has none of that and I really like it better for that reason.