Peter, if your girlfriend's jacket leaked I doubt it was due to the pit-zip alone. I would think it is either due to a poor design or perhaps even a factory defect of the jacket because afterall a pit-zip is a zip just like any other zip on the jacket (front zip, pocket zip etc). I see no reason why a pit zip would leak more than the front zip for example, especially while biking it would be the contrary and any goretex jacket has some kind of zip somewhere. The zip under the arm is no different than any other zips. I used both type of goretex jacket, first without a pit-zip and for the last 5 years I use a gorebikewear with a pit-zip. I would never buy one without one. This is so much better especially while going uphill. It feels so nice to feel that little wind when you start to get hot and sweaty inside of the jacket. Pit-zip actually increases the waterproofness of the jacket because the classic cause for goretex fabrics to leak is the accumulation of H2O on both side of the fabric. So when you are excersizing the goretex starts to leak when you have sweat accumulating on the inside part of the fabric and rain on the outter side. Since pit-zip increases the ventilation inside the jacket, it decreases the amount of perspiration built up inside the jacket therefore it decreases the chance that the jacket leaks. I would suggest you contact the manufacturer and see if they can do something about it, it is not normal that a new $200 goretex jacket leaks.
