I think its a great gadget. The MSR Miox ($130; www.msrcorp.com) is a brilliantly clever little device that uses salt and an electrical charge to create an extremely powerful germ- and virus-killer. You mix some untreated water with a dose of the salt, let the Miox charge that mixture with electricity, then add the result to your drinking water. Within 30 minutes it kills nearly all bacteria, protozoa such as Giardia, and viruses (cryptosporidia take longer to kill, about four hours).
As a bonus, the Miox is much smaller than a filterabout the size of a large whiteboard markerand can treat water for an entire party.
There are a few minor downsides. It doesnt filter water, so youll still have some grit, dead Giardia, and any aftertastes already in the water (the Miox solution itself is tasteless). Its not a drink now" method, so you cant find a cool stream, filter a quart of water, and have a sociable drink. And its electrical, so theres always the chance of a problem there, although its CR123 batteries last for some 200 recharges.
I wouldnt necessarily say the Miox is perfect for everyone, but it sure is an excellent alternative to bulky filters (none of which remove viruses, anyway, so still require extra water treatment in many parts of the world).
Check out this years more than 400 must-have gear items, including a comprehensive hiking section, in the 2006 Buyers Guide.