I've been trying the Sawyer Squeeze system since last summer:
http://www.sawyer.com/water.html#water1
Mine has 3 different sized mylar bags. They are a bit hard to fill from a shallow puddle (I use the cleaning syringe), noisy when squeezed, and can be punctured. They say that the filter can be attached to common drinking water bottles, but I have yet to find one that it fits.
But, they have other systems, based on the same filter, that include a replacement hydration pack.
Seems to filter everything and is guaranteed for 1 million gallons (not sure how you'd prove that though).
Pat