Water has so many health benefits, as listed by some of the other commenters here. Water hydrates our cells and keeps our system running more smoothly.

However....

Adding artificial flavorings and sweeteners can undo all the benefits of water. Look at the ingredients in most drink mixes on the shelf. You'll find stuff like:
Citric Acid, Sodium Citrate, Gum Arabic, Sucralose (Sweeteners), Contains Less than 2% of Natural Flavor, Sucrose Acetate Isobutyrate, Red 40, Blue 1, Yellow 6, Potassium Sorbate (Preservative).

There are sweeteners, preservatives, dyes and other chemicals... all taking away from the healthy properties of drinking water in the first place. ;-)

Yes, some people find the taste of water "boring." Adding a slice of lemon jazzes up the flavor AND alkalinizes the water, and making your system more alkaline has many health benefits. There are other ways to add flavor, such as floating fruit and herbs in a jar of water. Try a couple slices of cucumber and some fresh mint; a small slice of watermelon and a sprig of rosemary; a few strawberries and lemon slices; pineapple-mint-ginger is a good combination... the list is endless. A quick internet search for "flavoring water naturally" comes up with lots of great ideas. Mother Nature provides many fresh 'flavor boosters' that can also have healthy side effects.

Go forth and hydrate, y'all! :-)