I just use a Katadyn filter. Mine is rated for 10,000 litres of filtered water which for me seems pretty good. I also have a Steri-pen that I use when I am filtering river/pond/lake water as a double safe. So far have not gotten sick, and the water all tastes good.

I do also have the purification chemical just in case, but I don't ever use that. That would be a last ditch thing for me considering the other system I use.