distilled water is water that was steam, right?
That's right. Like rain.
you only get minerals n' shit from well/spring/etc. water, not rain water, eh?
wonder if that's important in any way (I'm thinking of Man Vs Wild type scenarios, where rain water might be the best you can get)
Basically, yes. Rain that falls on rocks like granite, such as the Welsh reservoirs that supply Birmingham where I grew up, or the streams in the Lake District that serve a lot of the local people (and reservoirs serving places like Manchester) remains almost as pure as distilled. Other than the issue of avoiding lead pipes that I mentioned, I know of no health hazards from this. I understand there is an issue with too-pure water leaching minerals out of concrete pipes such as the Elen Aqueduct from Wales to Birmingham, causing possible leaks, but that's an engineering issue, not a question of water safety.
If people really are deficient in minerals which they might get from hard water, then surely it's irresponsible to rely on pot luck for the minerals in the water. People in an area with water rich in calcium might suffer from magnesium deficiency, and vice versa. The standard skeptics answer to this would be that these minerals should be obtained from the diet (as in the usual response to vitamin or mineral supplements). If any minerals can't be obtained from diet for any reason, then surely that is a case for supplementation with the right minerals in the right quantities, not some random (and very small) supplementation which depends entirely on the content of the local water and the amount of water that a person drinks. I very much doubt whether such supplementation is necessary, though, except maybe in people with conditions such as osteoporosis.
The other possibility is that somehow pure water (i.e. lacking a few dozen parts per million of various dissolved rocks) causes harm as it passes from the mouth to the stomach (after which it is mixed with the minerals and everything else that have come from the food, so should no longer be a problem). I find this highly implausible, but if anyone has a mechanism for this I'd like to see it.
Edit: A fairly balanced article .. distilled is neither good nor bad for you so drink it if you like it ..http://www.cyber-nook.com/water/distilledwater.htm
And "Dr" Mercola telling you it will kill you ..http://www.mercola.com/article/water/distilled_water.htm
Otherwise, type drinking distilled water
into Google. Obviously avoid sites selling distilled water or distilling equipment, and those telling you it is "dead" and has lost its "vital energy".