Kevlyn:
I would probably define inanimate as something that doesn't move on its own.
Small quibble here: D&D alrady defines "inanimate". It means, simply: "not a creature" - not alive, not undead, not a construct, not an elemental, etc.
Also: water doesn't move on it's own. It reacts to physics. But if you put water in a bowl ... it's not going to get out of the bowl on it's own. (If it does, then it wasn't just
water, it was really
a water elemental - whole different ballgame.)
Personally, as a GM, I would have zero compunction about someone conjuring a glass of water. Yes, it would (briefly) quench your thirst - but it wouldn't count towards long-term survival needs,
e.g. if you're in a desert. If that conjured water is your ONLY drink, you're going to dehydrate and die.
But if you're drinking enough water to survive, and conjure a glass of COLD water for the sensation of refreshment? Bully. :)
As for how useful it is or isn't ...? Here's a few basic ideas for useful things:
A pot or pan - to cook when camped. No need to carry it around, and bonus: no need to CLEAN it after eating.
A coil of rope (you can get a godawful LOT of rope in a 3x3x3 cube of volume ...!)
A block of ice (chill EVERYONE'S drinks!!).
A shovel, pick, saw, or other rarely-needed but still useful hand tool.
A handful of sweets, with which to bribe/befriend village children. Won't ruin their dinner, 'cause it'll disappear in an hour!
A single coin, with which to bribe that vagrant/beggar/innboy/whoever (hey, if the money system hasn't changed since 3E: 1pp is a LOT of money to a lot of people).
A tinderbox.
A candle (hey, it's light for an hour ...)
And so on.