>In any case, I posted this thread hoping to gather some user feedback on the Sawyer Model 125 filter/purifier.
OK, I bit. I ordered both the Model 120 filter and the Model 125 purifier (actually the Model 135 purifier kit). When I get them I will report dry and wet weights and flow rates. There isn't a virus threat where I hike, but they claim a longer life for the purifier and if the flow rate is similar to the filter then I suppose there's no reason not to use it. (Anything that's going to clog up the purifier will likely clog up the filter, so that shouldn't make much difference.)
I do wish they had more technical information about the filter, but I suppose it is hard to state a 'pore' size in a non-porous design like this. Instead, they rely on their lab results. I find the claim of virus filtration to be outrageous, but I'm not going to argue with their lab results.
I normally use the UV Aquastar sterilizer (3.8 oz) for clear-water hikes; the Katadyn Pocket filter (21.6 oz dry) if the water is nasty; Aqua Mira (3.2 oz) in the winter for overnight purification (since I'm melting snow); and I always carry several Katadyn Micropur MP-1 tablets (4 tablets: 0.1 oz) in my first aid kit just in case. (The absolute lightest solution is if my friend Grant carries his filter :) I've found with Micropur MP-1 tabs that the water has no residual taste if it sloshes around for 45 minutes or so; just be sure to blow the fumes off the top of the water before drinking. Oh, for the days when all I carried was a plastic camping cup (0.7 oz)...