I see a lot of posts about Big Berkley, Katadyn, and others, but none on the $20 LifeStraw. After watching several videos about the LifeStraw, I bought a couple.
To start my testing, I hooked a clean inline fuel pump up with the Lifestaw at one end, a clear 5 gallon carboy at the other, and hose between. I used this to filter some rather murky pond water to see what would happen. I was surprised how clear the water was after filtration. I did prefilter it by running the water through a bath towel so that the large debris didn't get in, but what came out looked nothing like what went in. I drank some of the water and found it had taste, but was palatable. I also boiled some of the pond water for 5 minutes and compared the taste. The Lifestraw filtered water was considerably milder, but the flavor of both waters was the same.
The LifeStraw can only be cleaned by blowing back through the filter to empty it. You can't reach the filter like you can in a Big Berkley, so when it's plugged you simply have to grab a new one. This makes prefiltering very important. Because the filter does not remove all taste, I would hesitate to use 'any' water source.
For only $20 I would recommend this system to people on a tight budget and to those building bugout bags for large groups. I would recommend it to backpackers, hikers, and for temporary bug out bags. If you are preparing for TEOTWAWKI, the LifeStraw would be a great device for your day pack, but I'd still recommend a Big Berkley or other large water processing device for home base.