I've used it.
Effective against all 3 types of baddies -- viruses, bacteria and protozoa.
Easy to suck (as an inline filter)
Gravity feed option
No carbon element -- so foul tasting water will still come out tasting the same (may not be an issue if you hike in places with decent water sources)
Needs to be primed (flushed with faucet water using a faucet adapter) prior to use. Not just the first time, but anytime the purifier element has dried out (i.e. whenever stored in-between trips). If you don't flush prior to use, then it's extremely difficult to get water through. This is what happened to the reviewer you linked -- he flushed his purifier when he first got it, but didn't flush it again prior to his trip. Carrying a damp purifier means more weight and more mess -- but you will have to with this purifier.