Rating: 5 / 5
In the water purification vernacular, this is the best thing since sliced bread. These little Chlorine Dioxide tablets do in 20 minutes what other treatments can take up to an hour to do, plus kill most every water "critter" that is out to do your lower tract in.
Chlorine Dioxide tablets are not a panacea, as the water realistically needs to be somewhat clear and preferably 60F or more, but given that criterion, they work very well.
They are lightweight (well under a gram each) and readily available at popular outlets. Each tablet cost about 50 cents, and purifys 1 litre. As such, they can be more expensive than some other purification options for large volumes of water, and they don't remove solids or volatile compounds, but they do an excellent job.
If you're hiking where the water is relatively clear and not near freezing, these can be an excellent alternatives.
If you're solo or small group hiking, this is great. If you're going to be purifying scores of liters of water per day for a group, it may make sense to look at some of the lighter pumps.