Great addition, doubles the size of the tent
As others have sent this makes much more sense when added centred on the tent rather than the door, the instructions are wrong. We ran our gas fridge in the porch as it has plenty of ventilation, the gaps at the bottom were a bonus for us.
It adds about as much space as there is between the two bedrooms in the tent itself and means you have covered space. The door is vertical which means it won't rain in (unless it's really windy), We ran the gas BBQ one morning in the doorway as it was raining, but with all of the ventilation it was good. Otherwise it would have had to have been a cold breakfast :(