I love the GW, although I have the previous model. There are three caveats, though, some of which have probably been covered here.
First, *only* use clear-ish water. You can prefilter through a bandanna if you need to, which will at least remove the chunky stuff.
Second, *always* backflush. This is beyond simple...just lift the clean bag above the dirty, let it flow for a few seconds, and then clamp off.
And third, the ziploc-type seal on the dirty bag has always been a royal pain to close. We were hoping to use it as a (dirty) water carrier on dry camp days, but had to abandon that plan. I've heard other people complain about this, but I don't know if it's been corrected on the latest version (anybody?).
Liz in Seattle