Originally posted by leadbelly 1. Can I leave the Shake Reduction switch on all the time? If not, when should I use it? And what happens if I just leave it on all the time?
Pretty much yes you can leave it on all the time. You should turn it off if the camera is on a tripod.
Additionally, there have been some comments that at very high shutter speeds, the SR can actually make things worse. (That isn't my experience, though -- YMMV.) If your shutter speed is relatively high (see rule of thumb below), there's at the very least not much need for it.
Having it on probably has a negative impact on battery life, too, although I leave it on all the time and am perfectly happy with the number of shots I'm getting.
Quote: 2. How come I don't see much difference with the SR on? What should the situation be for me to properly use it?
Basically, you can use a shutter speed about twice or quadruple (that is, one or two stops) the length you'd normally be able to get away with. The rule of thumb for that is a shutter speed of 1/efl (where "efl" is the 35mm equivalent of the focal length of your lens) -- so for the kit lens, about 1/30th of a second at the wide end and about 1/80th at the telephoto end. With SR on, you might be able to get away with 1/15th - 1/20th in either case.
But again, your mileage will vary. How steady your hands are in the first place is a big factor, and "sharpness" is really a range of acceptableness. You might not be satisfied unless you've got much faster shutter speeds than that, or you might be fine with how things look at 1/8th of a second because you're only printing at 4"×6" anyway.