Eggs are a perfect protein as long as you eat both white and yolk. Those that skip the yolks are actually doing more harm than good, as there are things in the yolks that make the albumin in the white easily digested and assimilated.
A hard boiled egg uses up as many calories as it has during digestion and assimilation. So you can think of them as calorie-less!
Even tho eggs have cholesterol, there is no evidence to support the claims that eating cholesterol adds to blood cholesterol. Indian Yogi's have been known to eat nothing but eggs for protein and lived long and healthy lives.