I've been using the Brita Fill and Go bottles since about 2001. They are discontinued now, but I have several and a large stock of filter cartridges for them, so I'll be able to continue using them for years.
I've also tried the Pure Water 2 Go brand filters; I got a pair of the interts for standard water or soda bottles and tried them on my last trip to WDW. They fit nicely in a Dasani bottle, which I put in my carry-on empty, then filled at a drinking fountain once I got through security.
Both types of filters work great. They make the metalic-tasting water at WDW and turn it into something similar to Deer Park or Crystal Geyser bottled water.
I've also used my Britas outside of WDW, where the water has a terrible sulfurous smell and taste to it. The Britas filter out all of that and make the water fresh and crisp.
If you're picky about the taste of your water, I can highly recommend the filtered bottles. They're no good for removing bacteria, but if you just want to make tap water taste better, they are hard to beat.
Keep in mind that you can refill these bottles even from the sinks in any bathroom, as well as at any drinking fountain, and you can get ice and water free from any TS or CS restaurants.