The Sawyer Squeeze and Sawyer Inline both filter to 0.01 microns absolute. They are basically the same filter. Both can be set up as part of a gravity system (no pumping, hooray!). They also have one that filters viruses, but that's also very prone to blockage. Viruses are not a problem unless you're downstream of human settlement, in which case I'd use chlorine dioxide for the viruses and then filter for the bigger stuff (especially protozoa, which can take as long as 4 hours to zap chemically).

I would not waste my time or risk my health on methods not recommended by the Centers for Disease Control. Your Mileage, of course, May Vary. I've never had giardia but my dog has--after spending half a day cleaning up my car after he "exploded," I treat most of his water, too!

After having a friend get a nasty case of giardia (confirmed by lab tests) after a trip in which the only time he didn't treat his water was where the spring was coming out of the hillside, I hesitate to suggest not treating except in emergencies. He was super careful about sanitation, too. It turns out that the camping area in question has been popular with hunters for many, many years and the ground water there is probably contaminated.

I've also hiked farther up what looked like a pristine mountain stream only to find a dead deer lying in it, another reason I treat nearly all my water.

Again, Your Mileage May and probably will Vary!

Re sanitation: Frequent hand-washing and use of hand sanitizer, especially after "potty" breaks and before handling food, are important to prevent Norovirus (a true nasty, prevalent on the Appalachian Trail last spring) and other infections. Also, if you get sick during your trip, it's probably not giardia, which has an incubation period of ~10-14 days. There are plenty of other bugs (e. coli and the above mentioned Norovirus) that can make you just as sick, but they are far more apt to spread through lack of handwashing than in the water.

Do note, in an emergency, that dehydration can kill you quite rapidly. Go ahead and drink whatever's available in that case. If you get sick from the water, it won't happen until you get home and are close to medical care. If you don't drink, you'll be dead before you get home!