Product review (5 stars): Works just as well as the old
First, I'll state my bias here: I think these water filters are a big pile of crap and I think it's ridiculous of GE and the other manufacturers to have them in their refrigerators.  And I think it's absolutely obscene that GE charges $40 for each one.

So that said, I can't tell any difference between this and the GE MWF filter it replaced on my 2009 GE fridge.  You have to run a couple gallons out at the start to get all the charcoal dust out, but other than that it went in fine and I can't taste a difference in the water.  I've only had it in there a month, so I don't have a comment on how long it lasts - it says 6 months, but I believe that's just manufacturer-speak for "please send us money every 6 months".  I'll try to update this if it goes bad sooner than I'd like.