First, what is a polarizing filter? A polarizing filter is a filter used to polarize the light. In other words it will take the glare off of shiny objects just like polarizing sunglasses. It does this by redirecting light (usually) at a 90 degree angle. It also helps to enhance blue skies. And although they work as advertised, too often photographers allow these filters live on their cameras because the salesman* at the camera store who sold them that filter told them to. The problem with this is that you will be loosing 1-2 stops of light all the time. While photographers are constantly trying to gather more light by purchasing more expensive lenses, a polarizing filter cuts down the light all the time. So use your polarizing filter only when you really need it; like when you are on a boat in the middle of the day. Don't let it live on the camera. What about the blue sky? That's what photoshop is for!
*A note about camera salesmen and camera stores. Very often we find the Photo Police like to congregate at camera stores and sometimes they are dressed as camera salesmen.