Product review (5 stars): Works well, and now I know what these filters actually filter from the water!
I purchased this filter (like many here) as a lower cost alternative to the OEM GE filter.  Just a few days ago, I also purchased a water tester to test the water from our reverse osmosis system under our sink (it measures total dissolved solids and give a ppm number).  After putting this filter in our fridge and running a few gallons out of it, I tested it and found it had the same TDS as tap water (approx 500ppm).  I asked a question here about how these filter, and someone named Richard gave me the PERFECT answer.  For some odd reason, Amazon chose to remove his answer.  So for those of you wondering about the difference between a reverse osmosis filter system and this (a carbon filter) here is what Richard had to say:

"Fridge filters are carbon block filters that are used to remove chlorine, sediment, and VOCs. Carbon block filters do not remove TDS (Total Dissolved Solids), which are made up mostly of salts and minerals and also inorganic contaminates like arsenic or barium. Therefore, using a TDS tester is not a good indicator of the performance of your fridge filter."

Very useful information and I am not sure why Amazon removed it.  So, in summary, these fridge filters remove non-solids like chlorine but do not completely clean the water.  In my case, I should hook the fridge water line to the RO system (tested 20ppm TDS) and get perfect water from the fridge!