I drank a lot of Poland Spring when I was working in Massachusetts because that was the ubiquitious brand. I really didn't care for it that much, though, because of the sodium content (they don't add sodium, but it has a certain amount that's naturally occurring). I prefer Evian, but it usually costs about 50% more than the local regional brand.
Of the two national brands (Coca-Cola's Dasani and Pepsico's Aquafina), I prefer the Aquafina because I like the large mouth of their one-liter bottles. Much easier to chug than the narrower mouth of most conventional bottles.