Well, it's my understanding that theres a "rule of thumb" about the softer the water, the better.
Here in the southeast of the UK, we have quite hard water i.e. with quite a high calcium content (lots of scale in the kettle and coffee maker). Though if you look around you can find bottled water (locally bottled) that has a lower calcium level. The originating spring being located in one of the few sandstone areas.
If you really want total control over your resulting product, then distilled water, re-oxygenated in someway (air pump?), then adding all the nutrients, minerals, etc etc yourself.
Hell, you can get really anal about it, sourcing specific honeys (and yes you appear to have a much greater choice in the US), as well as testing acidity etc etc.
I'd guess that it depends on just how far you want to go.
I've made mead with local tap water and the lower calcium bottled water. My honey is mostly sourced from the local supermarket (which means it's a blend, that is probably already pasturised). Hence I don't boil it - I don't usually heat it at all other than to make it easier to remove from the jar.
So far, I've used high alcohol yeasts mainly and thats resulted in the same issue already highlighted by mgayer (and it's also mentioned in Ken Schramm's book "The Compleat Meadmaker") though mgayer says "medicinal", whereas Ken Schramm likens it to "Listerine".
I do, currently have 3 one gallon batches of an identical recipe but using 3 different Lalvin yeasts. Not that I'm trying to be any kind of perfectionist, I'm just trying to find a recipe that is straight forward to make and doesn't necessarily need to be aged for 12 months +
From my reading "around the Bazaars", it seems that it's best if the honey is unprocessed, so that any heating removes hive debris etc, with soft water (though free from process additives like chloramine and chlorine).
I doubt whether I can achieve that, but I'd keep looking around to see whats available.
TTFN
fatbloke.