Sorry, shrike, I DID read the Steripen Adventurer manual very carefully both before leaving home and at the creekside when the thing wouldn't work! My son, an electrical engineer with a background in electronic testing equipment, also read the directions carefully and had the same problems. He could turn the thing on and off, but the switch was too stiff for me! But he also had no success with the problem of the thing cutting off in mid-cycle. No, the red light we got was definitely not the low-battery signal. And yes, we were very careful to keep the UV light submerged while stirring.

After I posted my original report on my problems with the Steripen on this and other forums (summer of 2008), I got a number of responses reporting the same problems. So it isn't just me, and it isn't just people who don't read and follow the directions! I've since seen a number of posts from folks who found the Steripen did fine at home (as did mine) but malfunctioned in cold weather or at high altitudes.

Please don't cavalierly dismiss all authors of adverse reviews as "people who do not take the time to read the manual." Maybe you just got lucky and happen to have one that did not act up in the conditions in which you used it. Maybe I had a defective model, but it worked fine at home with tap water before and after the trip. I could even turn the switch on and off at home, although I couldn't manage it out in the field--evidently at 80*F it's a lot less stiff than at 50*. Unfortunately, I generally backpack under colder conditions and where tap water is not available.

After a number of trials with different gravity filters (the one I like, the ULA Amigo Pro, is no longer made), I'm going to emulate Phat and stick with chlorine dioxide. Lots lighter, lots less complicated--and batteries not required!