I have the Sawyer gravity-fed filter system, it's basically a camelback-type of bag with a filter that attaches to the tube. You hang the bag and let it go.
I like it because you don't have to pump it, you can fill the bag, throw it on your pack and when you find a place to take a break, hang it and filter your water. You can actually put the dirty water bag on the top of your ruck and your clean water bag/bottle on the bottom of your ruck and let it go while you're walking around.
Their filter is also a lifetime filter, you run water through it in reverse once in a while to clean it, but that's it.
I modified a piece of drinking tube with a camelback quick disconnect on one end and a Sawyer quick disconnect on the other end so I can hook mine directly up to my camelback bladders using the drinking tube. That way, it's a closed system, so I don't have to sit there with it to ensure that nothing (bugs, leaves, dirt, etc) gets in my clean water bags.
As far as water purification tabs, I still take some along - s**t happens, stuff breaks or gets lost. They're light and relatively inexpensive, so there's no reason why you should be having to choose between dehydration due to lack of water or taking your chances with dirty water. You don't need a month's supply, you just need a couple days worth to get you back to your truck/car/home.