Weighing in as an ultralight water purification method, the Aquatabs from MSR remain a great portable option. They treat against bacteria, viruses, and giardia cysts, but not cryptosporidium. These tabs are a great backup purification method to carry in your kit in case your primary filter method breaks down, as they are lighter than Aquamira Water Treatment Drops. However, the Aquamira version is not as versatile for different volumes of water.
Since we last reviewed these tabs, MSR has updated the packaging. We've contacted the manufacturer, who has confirmed that the product has not changed whatsoever since we last tested them.