I've been using a Sawyer filter for the past 15 months, and it's been great. I did have to replace the Sawyer pouches, because they're not very durable; I had two start leaking pretty early on. On my last trip (one week), I took a pair of the Evernew pouches, one liter each, and they worked out quite nicely. It was nice having two of them along, because I could fill them from a stream and then set them in the sun to warm up when I wanted a non-freezing sponge bath :)
That said, the filter itself has been fine. I haven't had to backflush it yet, either. I like the Steripen idea, but the fact that it relies on batteries and tends to eat them made me start to mistrust it. It failed on me even with fresh batteries in it, and even though I'd put one in backward when I replaced the batteries, it didn't work when I needed it. I put new batteries in it when I got home, and it worked fine. I stopped using it after that.