Goretex is waterproof to the extent of its mission.
The real challenge with goretex is that it relies on pressure and temperature variation in order to get the vapor to move through the barrier. Kind of like high pressure moving naturally into a low pressure area.
The same principle applies with goretex. The water vapor/humidity inside your jacket needs to be greater than the pressure outside the jacket in order for the vapor to pass. So if you are really working and hot and it's cold out then the vapor will push through the barrier. If the internal temp of your jacket is the same as the external temp then there's nothing going on to push the vapor through the membrane.
If the exterior of jacket gets wet then the vapor can't pass through anyway.
In the end there's one principle that overrides all: the trick is to stay warm when wet. one way or another dampness is going to invade inside the jacket whether it be condensation or otherwise.
