Well I now have the 1A charge thingie supplied with the iStick30w. What I've discovered is that the istick gets warm while it's charging, but the wallwart does not. When it stops charging and the display goes off, by the time I realize that and go unplug it, the istick is no longer particularly warm. So I think me and my iSticks are safe. Of course I've never let it run down beyond 2 of the flashy squares in the display; when it's only one of the squares, then it doesn't even get terribly warm.
Andria
I think if discharged to only about the half battery level indication and no lower, it will generate only a little bit of heat. The one time I let it mine go until it quit, it got much warmer on charging. Also on that drain, the 2nd half of the battery level indicator seemed to go rather quickly. I take that as an indication that that half way level is actually below half the battery capacity...more than half the capacity used up at that point.