The beauty of this pen-shaped unit is that it’s so lightweight you won’t know your carrying its 3.5 ounces. The downfalls? Well, for starters it doesn’t filter your water, so if you’re not careful while filling a bottle prior to purifying it you could wind up with all kinds of interesting things floating around in your drinking water. Oh, they’ll be dead and purified, but do you really want a meal in your water?
The second problem I noticed might simply have been operator failure in over-doing the purification. Whatever the cause, the water had a strong, chlorinated taste. Kinda reminded me of a two-tablet system I was introduced to when I first started backpacking way back in the last century — you had one tablet to purify the water, and another to give it a palatable taste.
The rest of the post gives the impression that there’s not much of an advantage over carrying tablets or small bottles of chemical purifiers.