The difference in glycemic index between fresh fruit and other sugars is significant. I tend to be highly sugar reactive and stay away from sweets and even processed carbs (ie, white rice) to avoid the crash that follows (headache, shakes, hunger, etc). However, I can plow through 8 - 10 mangoes a day for a 2 month period of time with no ill effect. The only issue I get is "melon belly," where my belly aches if I overdo it (ie, 5 mangoes in one go) without eating anything solid in between.
The other interesting aspect is that fresh fruit consumption doesn't really contribute to cavity development (unless the fruit is highly acidic). I can notice a very distinct difference in plaque build-up from eating sweets vs fresh fruit (the former contributes to plaque, but usually not the latter).