I carried an MSR Waterworks filter on my last tour (3 weeks in Central Colorado, combination of dirt roads, hiking, and a little bit of singletrack), and was pleased with it. It takes about 1 minute per liter, and the ceramic filter is easy to clean when it gets dirty. It's a bit heavy (18 oz or so), and if I was doing a short tour (2-3 days), I'd probably just take chlorine dioxide tablets. Those take about 6 hours to be effective, and I wouldn't want to use them for more than a few days, but they're a lot lighter than the filter.
The only time I've ever used wild water without treating was when I found a spring along the Blue Ridge Parkway, and a local road cyclist assured me he drank the water from that spring regularly without a problem.