Usually, nothing gets stuck in the ports, save for dust - but a little cleaning can fix that.
Porting a slide/barrel also makes them lighter, allowing for faster cycling.
Real steel information straight from wiki:
Porting involves creating ports or holes that are precision-drilled into the forward part of the barrel (and slide on pistols). These holes are designed to divert a portion of the gases expelled prior to the departure of the bullet in the direction that reduces the tendency of the firearm to flip upwards. The concept applies Newton's third law: the exhaust directed upward causes a reciprocal force downward. Porting is most commonly used on shotguns, where recoil is most significant and makes rapid firing difficult. Even single shots of magnum-strength loads are uncomfortable for all but the most-seasoned shooters. Porting has obvious advantages for faster follow-up shots, especially for 3-round burst operation. However, in most instances porting does nothing to enhance the accuracy of follow-up shots.