The water here in San Antonio is so hard it tastes weird. Reverse osmosis seems to be the main thing I need, and filtering out some chlorine taste is a benefit.
Why pay $1/gallon when walmart has a dispenser where it's charcoaled, RO'd, UV'd etc, for 37 cents a gallon? I mean, if you have to buy it, you might as well look for the cheapest option.
And often, the cheapest option is to fill your bottle at the filter at work before you go home. :)