many people do not like sneak, but if you are sneak-minded player, it is a very powerful tool.
it works like this: based on your skill, and perception of people around you, you must be a MINIMUM DISTANCE AWAY from someone (the amount of distance depends on skill/perception/direction) to become invisible.
medium-low sneak builds can be good at long range because they are invisible from afar.
high sneak builds often incorporate melee attacks or pistol attacks to capitalize on the ability to sneak much closer to an enemy.