oooph...I'm really glad all of you have had such good luck with your steripens..I am waaay to sketched to use one myself. Sure, Giardia (and maybe Cerpusculum) may be killable with UV, but it's the chemicals I'm worried about (Hepititus, pharmaceuticals, etc). 2, I don't know that I like to rely on stuff that uses power. A flashlight, ok, my water purifier...? I do quite a bit of hiking and packing in semi-urban areas. I use the MSR Sweetwater filter and back it with the MSR purification drops. Call me paranoid, but I haven't gotten sick yet.