I loved it when it worked, but when it didn't it was a waist of time, money, and effort. I'm currently seeking repairs.
I purchased this purification system on pro-deal so the risk of a new product was somewhat mitigated by the excellent price. The SteriPen uses concentrated pulses of UV light to scramble the DNA of any cells within a small circumference of the bulb, making it impossible for any protazoa, bacteria, and even viruses present in the bottle to reproduce after treatment. Despite its 'magic wand' appearance, it is known to be one of the most effect treatments on contaminated water. It is a method frequently employed by commercial water purification plants. Take special note that this doesn't filter anything out of the water, so it is effective against organisms that might make one sick, but not murky or tanic water. Also, it should be noted that its effectiveness on organisms is severely diminished in water that is not sufficiently clear. Still, within its field of use, this item should be a dream come true. It takes 90 seconds to purify water, leaves no chemical tastes, and weighs less than any filter I know of. I used it during a one week backpacking trip to Michigan's Pictured Rock National Lakeshore and brought it to the UK to purify my water during my 2 1/2 month hiking tour of the country.
Durability is the point here. Even a working SteriPen is a piece of gear to be cautious about. The fact that a simple electrical failure could result in the total failure of my purification system is a fact to be carefully considered. When it works, oh boy, but when if it fails, it's dead weight. It worked very well in Michigan, but the next year when I took it to the UK it failed to sense when it was submerged and so failed to activate. I ended up carrying it with me for a month before sending it home and using iodine instead. I have since used a friend's standard SteriPen on a couple of day hikes and overnights. He has been very happy with his SteriPen and convinced me to try to have mine repaired. I will emend my review once I have received it back. Regardless, I don't know if I can ever trust it again. True, I can always boil my water, I've done it during a two week wilderness trip in Michigan, but I don't like to. Be cautious.
If it works its one of the most efficient and exciting pieces of gear I've ever used. Of course, it only works with clear water, but that's mostly what I travel in. It's fast, results in some great tasting water, and is extremely light and packable. Unfortunately, it failed me after only one week of use. At that point it becomes the most inefficient piece of gear in my pack: a dead weight that I carry around in hopes that when I get back I can replace it. Thus for week one it was one of the best pieces of gear in my pack, significantly increasing the quality of my trip. Week two, when it failed, it was quite the opposite.
At this point I'm wholly unsatisfied with the value of this product. Once I receive it back from being fixed, and if I can bring myself to trust it again, I will be able to comment further. Still, with the risk of catastrophic failure and my anecdotal experience of such a failure, I can't say that I personally recommend this water purification system. Even if it turned out to be a generally dependable piece of gear (I mean, if my experience were a fluke) then I would still caution anyone from depending upon it since electronics are the most difficult things to gauge and a catastrophic failure of the gear will make it useless.