This is a topic that can cause great dissension, because it comes down to personal taste.
Steve has no problems drinking the tap water at our house. I swear it has a "taste" to it and can't drink it unless I get it from the refrigerator water filter. I can even tell when it is time to change the filter before the light comes because the water starts to get a taste.
Using a water filter for people like me, who swear they can taste a difference in tap water, can save lots of money compared to buying bottled water. Bottled water can range from ~$0.50 a bottle to over $2 a bottle! I am not saying to never buy bottled water, but for everyday use buying bottled water can be a huge expense.
I have several reusable water bottles that I fill-up almost daily. I try to use one even if I am going to be home for the day so that I can make sure I am drinking enough. I take one with me when I am out running errands, I take one to the YMCA, I take one to work, I have even been known to take one to church.
I will admit that if you were to visit my house you would find a case or two of bottled water. I keep it on hand in case we are traveling to keep in the car, or in case of an emergency and we don't have access to clean water. But, the bottom line is that a small investment in a reusable water bottle and a water filtration pitcher or faucet attachment can save you money in the long run.