I think the sugar crowd should try some specialty beans, roasted well (i.e. not burnt) and see what flavor you have been missing out on this whole time.
None! Although sugar is tasty, it has horrible long term side effects on the body. So I'm big on limiting sugar when possible, but not unrealistic in saying I never intake any. it's just not often.
Since I drink coffee most days, I choose to never put sugar in my coffee so I limit my overall daily intake.
I do not take sugar in my coffee. Just lots of milk. Sometimes it's more about the caramel color than the taste. I do not like my coffee too strong or too bitter. Just warm and comforting.