It has long been a pet peeve of mine that it's so difficult to get good instant coffee in the US. Even brands like Nescafe, which are perfectly drinkable in Europe (and, I'm told, in South America) feel the need to sell swill to the US market: a thin, harsh, acidic brew that tastes like it was underbrewed then burnt. Maybe they think that's what we like.
So it was with trepidation that I tried Starbucks's new offering, Via, specifically their Italian Roast. I'm somewhat pleasantly surprised. It's not perfect: it tastes burnt to me. But it's reasonably full-bodied, and it's not acidic. It even has an OK aftertaste. It's actually quite acceptable as an instant coffee, and I'm willing to believe that the burned flavor is their idea of an Italian roast (that is, it's intentional, not accidental). A little one-dimensional, but acceptable as a substitute, and probably quite useful for things like coffee ice cream.
Doing a little digging, it looks to me that Via is actually a combination of traditional instant coffee (that is, brewed coffee that's been freeze-dried and powdered) and powdered coffee beans. This is clever: It's like making a super-smooth (but thin) Turkish coffee for the oils and other more obvious flavors, then making up the rest of the flavors that we don't notice as much with a probably very muted brew. (In this way it's a bit like karaoke: there's a background flavor trying as hard as possible to be inoffensively competent, and most of the effect comes from the predominant flavors that are added on) Because the coffee is ground so finely, I'm guessing that the extraction of flavor is basically finished by the time you finish pouring the water, so they don't have to worry about you tasting it too soon, or leaving it on your desk too long. (As an experiment I let the dregs sit for half an hour before finishing them. Not quite as good, but not horrible)
Anyway, I guess my recommendation is, if you periodically find yourself with access to hot water but not decent coffee, find a flavor you like and carry it with you... but don't use it unless you have to. (You'd still be better off carrying K-cups, scissors, and a funnel, but this is not always an option)