Cycles Ambient Occlusion? Do I really need/want it?

Do I need this option on for ambient occlusion in cycles to work? My issue is that it just boosts the environment light and does not seem to do anything else -_-
I could see myself using it now and then to brighten things up, but seriously, is that all it does? I’m under the impression that ambient occlusion is an ingrained part of the way cycles renders things and that this option is just poorly named. If not, why is there no multiply option like in BI?

Anyone here know enough about cycles to answer definitively?

You don’t need ambient occlusion in cycles. You may occasionally want it for some particular part of a material, but just because it’s there doesn’t mean you need to use it. BI doesn’t have global illumination so it uses fake effects like AO instead. Cycles doesn’t have this limitation, so AO is only necessary when you want to take advantage of something that fake effect offers.