Product review (3 stars): Not sure about the 6 months or 300 gallon rating...
I'm giving this 3 stars for now.  I ordered mine 5 months ago and for the last 2 weeks my water has started coming out in a trickle.  I think it is the filter, but if I buy a replacement and it doesn't help I'll update my review.

UPDATE 9/4/14 - Lowering my review to 2 stars.  I replaced the filter with a Samsung filter and the water started flowing well again.  While the other filter did cost about ten dollars more it is NSF 53 certified, not just NSF 42, and I value that for my health.  If that doesn't matter to you then this can be a value, but I don't expect we came near 300 gallons as we have another filtered tap in the kitchen next to the sink and it gets far more use, so changing it at 5 months raises the effective cost to me.

UPDATE 12/20/14 - Restoring a star.  The Samsung filter that replaced it started doing the same thing - in about 8-10 weeks. Again, I have a softener and a Culligan pre-filter, so I am starting to wonder if all the filters for these refrigerators are junk.