for a guy in the bottling business, my personal opinion is that if the bottled water is "safe" for consumption, then it's basically personal taste preference that determines how much you want to be ripped off for the bottle and the source.

By "safe", I mean that the water should be free of microbial or organic content, have a low TDS, and metals concentrations below your typical North American water quality standards (i.e. as close to zero as possible). I'd also look for something that is disinfected by UV and has a shot of ozone in the process as I don't like critters growing in my water as it travels from plant to my mouth.

For those of you who have sensitive taste buds, keep in mind that the "purest" waters (those that are either processed through steam distillation, or else RO filtered) have no inherent taste. What you are picking up is probably organic residue left over in your mouth that is "activated" by water contacting your salivary gland (sour-mouth).

Mineral waters (re-mineralized or naturally mineralized) can obviously impart a slight but noticeable taste and mouth-feel, but i'd be shocked if more than 0.1% of the general population can differentiate between mineral waters.

One other thing to keep in mind is that the PET bottle is porous... the age of the bottled water can slightly alter the taste of the contents. Glass bottled water is better at weathering age, but most of these are capped with a metal closure that isn't truly airtight.

In a nutshell, remove the crap and pretty much every serving sized bottled water is worth about the same - about 15 cents for the processing and PET costs. Anything above that is just profit in the pocket of a very shrewd marketer.