Rating: 4 / 5
It's not a 5 because it's heavy (about a pound). Otherwise, this is a great product. It filters quickly, it's easy to tell if the element is worn out or damaged or simply needs cleaning. It has an excellent integral charcoal filter that removes bad tastes leaving you with some of the best tasting water anywhere. I always chlorinate my water before filtering to kill viruses that the filter can't catch so the charcoal feature is especially important to me because it removes the chlorine after it's done its job.
The pump lever gives you plenty of mechanical advantage so filtering is fast and easy. The pump started to squeak after a few hikes, (a common complaint apparently) but I remedied this with the recommended silicone grease.
When the filter finally became clogged (about 60 liters of clear water), a very light scrubbing with the included scrub pad restored it to like new performance. Some of the ceramic filter element is worn away in the scrubbing process necessitating eventual replacement. A wear gauge that stores in the bottom of the filter enclosure lets you know when it's time to replace the element.
The filter has one harmless idiosyncrasy. It doesn't get harder to pump as the filter becomes clogged. It just pumps less water. This is because it has a relief valve that shunts water back to the supply side if there is an over pressure. So unless you're watching carefully, you can be pumping for a while before you realize you're not moving much, if any water.