First off, the suit fits amazingly well. They are form fitting and barely feel like wearing anything once worn for a while. The suit will absolutely keep you warm under layers. Even at 20-30 degrees, wearing this under a jacket was almost too warm. The rear waist zip works great for bathroom breaks, just don't forget to zip it back up.
My neighbors may think i'm a bit strange running around the yard dressed as a ninja, but cool weather calls for comfort.