I was lucky to win a Sawyer Water Filter a few weeks ago as part of Kieth Fosketts' Blog. The filter is good for One Million Gallons, is easy to use and clean. It is also very small.
I was disappointed this was not compared in the recent TRAIL magazine, all the others noted went to maximum about 500 Litres. For the money the Sawyer wins hands down. Pumping Filters may have a benefit over actually getting the water from a stream or pit. However, Sawyer has a bag to bag gravity system, the dirty bag can be filled very quickly dragging this through the water.This can be done with any bay system with a large opening, say Camelback.
I have used this a little so far but will give some further reports which I hope will back up my initial findings.