Katadyn knows water filtration. It's all the Swiss company does, from trail portable systems to full desalination, and they've been doing it for a while now. Their latest personal system is the BeFree water bottle, a great solution for fast and light and just in case.
The BeFree weighs just over two ounces and when empty the 0.6 liter bladder rolls up around the filter into a roughly 2x3x4 inch package that fits easily into a coat pocket. Of the three bad things that might be found in water - protozoa, bacteria, and viruses - the 0.1 micron microfilter on the BeFree will take out the first two, which are generally 0.5 microns or larger. Viruses require a purifier rather than a filter, and luckily are relatively rare in North America anyway. If viruses are a concern boil your water or use chemicals.
The primary advantage of the BeFree is that the filter separates easily from the bladder, so you can dip the bladder in a stream or other water source without exposing the drinking tube to the potentially dirty source water. A few twists and you're back in business: just squeeze or suck and you're good to go. Notice my maturity in not inserting normal male sex humor there. See, we can be trained. A big secondary advantage is the ease of cleaning: instead of a tedious backflushing process, you can just shake a half full bottle to clean the filter, or remove the filter and swish it in some water. Done and done. If you really want a traditional backflush you can do that too by simply unscrewing the white cap from the blue filter base and putting under a faucet with known good water.
The Katadyn filter actually uses a Hydrapak bottle, which imparts only the most minimal taste to our palate. Apparently some early production runs of the bladder had some problems with tearing at the seams, but ours had no such issues. The manufacturing process was changed and additional quality controls implemented, and if by some outside chance you end up with a defective bladder Katadyn will replace it. That said it is a flexible bladder, and If you tend to be hard on your gear you'll probably want something equally hard to push back, but in any case the ideal use of the BeFree is fast and light.
The primary limitation of the BeFree is the small capacity bottle that comes with the filter, but there are other compatible higher capacities available such as the 3L Hydrapak. With the smaller bottle the use of the BeFree is limited by your access to water: less access means shorter trips, and the more access to refill opportunities you have the longer you can go. If you're trail running a long pass with a stream nearby the BeFree would be perfect. Overall we appreciate the quality, simplicity and ease of use of the BeFree. It frees you from carrying a bulkier pump or foul tasting and time consuming chemicals, and given the right situation that means more fun and less fussing around.