Ben T.wrote a review of Platypus GravityWorks 4.0L Filter System on April 19, 2014
Familiarity: I've put it through the wringer
I will never use a pump filter again after using one of these. No more crouching by the creek furiously pumping water into Nalgene after Nalgene. Just fill the dirty water bag up, hook it up to the filter and clean water bag, then forget about it for a couple minutes, boom 4 liters of water.
We used the gravity filter on four day trips for 15 weeks. It never failed us, never got clogged, and with 4 people we always had enough water. When water began to get scarce up high we could use the bags to carry 8 liters of water up to camp. Like previous reviewers, you need to be careful of the filter freezing at night. As far as durability, I hauled mine all around Thailand and Cambodia in the bottom of my pack for 7 weeks and it still works like a charm.