Product review (4 stars): Costly cartridges.
I've had mine for about six years, without problems, and the water tastes better through it.  I don't know why the replacement cartridges cost more than the whole filter unit, $2 more at last check.  My unit is actually a countertop filter (hole drilled through sink, chrome spigot) that no longer seems available, but it uses the GXRLQR filter cartridge and the same GXRLQ housing (mounted under the sink).