The filter does not remove bacteria, cysts or viruses, so it can't be used to purify stream water. It should only be used on potable, safe water sources. You can't use the bottle with sports drink or flavored drinks, as the filter will filter out the flavorings and sugar, etc. You can only use it with water.
The bottle comes with a replacement filter. Each filter should last for 48 gallons of water, or about three months.
I know many people who avoid tap water just because of the chlorine taste or the particular odor or taste of their tap water. Rather than drink extra calories, artificial sweeteners, chemicals, etc. it is usually a good move to find a way to make tap water palatable. When out walking, it saves money and trash/recycling to be able to fill up at water fountains and taps along the way.
The wide mouth of the bottle makes it easy to add ice. Cold water is usually more refreshing. It may be easier to wean yourself away from flavored drinks if you drink cold water rather than lukewarm water.
Drinking and Carrying
The top of the Groove has a big wing with a large thumb-hole for carrying on the crook of a finger or attaching to a pack with a carabiner. I don't recommend carrying water bottles in your hand while walking. That can cause strain from neck to elbow to wrist. But many of my best walking buddies do so anyway.
The Groove is bigger around than I like to carry easily in my delicate, lady-like hand. I am more likely to carry it in a pack or in a sleeve of a water-carrier fanny pack. It also makes a good bottle for keeping on your desk or work station at work or school. It fits into the cup holder in my car.
The Groove comes in a 20 fluid ounce version, which should be enough water for an hour-long fitness walk. Drinking recommendations for distance walkers
Cleaning and Construction
The bottle has a wide mouth, which makes it easy to add ice cubes and to have good access for cleaning. The non-insulated version is dishwasher-safe, but only the cap assembly (other than the filter) is dishwasher-safe on the insulated version. For those who prefer to get away from plastic altogether, there is a stainless steel version.