The US, and many other governments, regulates the quality (safety) of tap water. If you're on a well, it may or may not be regulated properly.
I don't care what is said about tap water vs. bottle water... some tap water tastes like absolute shit (and some bottled water, too), and I could care less if it's "safe". Safe is good- but if it tastes terrible where you are, then it tastes terrible.
At least in the US, bottled water still has to pass minimal safety testing.
So really it comes down to taste. Depending on where I am (and I love drinking water), i either enjoy it from the tap or find it horrid-tasting. That's just a personal preference.
And poke fun at Evian all you want... I don't care what they claim, I don't care if it's really the purest water on the planet (or not)- it tastes good to me, and I will buy it however often I feel like it.
I have to have good water, though... I have a really good purifier hooked up to the tap. I fill 2-liter bottles (not old soda ones, they're a different shape), one at a time, and keep them both in the refrigerator. I rotate two, so while i'm using one, the other is sitting in the back for a few days, and the water tastes that much better.