Product review (5 stars): GE MSWF Refrigerator Water Filter
This product works as stated.  I replace my filter every 3-4 months, as we drink a lot of water.  I believe the manufacture recomends every 6 months or so many gallons, and I think I exceed that.  You can tell the difference when you replace a filter that has been on for too long.  Great product, but make sure you shop around for the best price.