Depends on the trip and mode of transport.
My most frequent trip is actually an overnight backpacking trip to a specific spot here in MD. I know the water, and I drink straight from the source.
On backpacking trips, I prefer Polar Pure iodine prills. Stupid-simple to use, and I personally don't notice the taste after about the 3rd quart... some people never don't. If you put something acidic in it, like lemonade mix, that sort of neutralizes it. I used to use Aqua Mira, which is a couple ounces lighter, but got tired of fiddling with 2 chemicals.
On canoe trips, I have come to love a Platypus GravityWorks system. I have the 2L bag, and it's perfect for my solo trips. With others, the 4L would probably work better.