Well, the shots aren't really
impossible, just sharper. But it's hard to say which ones are much different without taking it w/ and w/o... some days it's easier to handhold a longer exposure than others!
I have some experience in going from no IS (on my original DSLR, the *ist DL) to in-body IS (on my K100D) and it definitely helps - I think I clearly got better on-ride photos by having a
stabilized 50mm F1.4 than the same lens on my DL w/o IS. Also more good nighttime handheld shots.
OK, you asked for examples... let me see if I can find any from
Disneyland. (I didn't have the K100D on my last WDW trip.)
Here's one. Not a terrific photo but a good example.
Tamron 28-75mm F2.8, 28mm, F2.8, ISO 1600, 1/6th second.
It's hard to tell from the web-sized version, but viewing it larger (
here it is at 1280x854), you can see that the building is quite sharp - the high ISO cuts that a little bit but there's no "shaky hand" motion blur that I can see. Now, without IS - there's no way I could hold a 1/6th second shot and get a result that sharp, even at a relatively wide 28mm.
From a quick glance, I don't have that many other shots, as I usually used a tripod for night shots, or was deliberately keeping the shutter speed up. I'll try to keep an eye open for them. I'm sure that I have a few non-Disney ones.
I'm not sure if it's over-hyped or not. It's certainly not a magic bullet and only good in certain circumstances (won't help when taking pictures of active kids, I can tell you from experience), but when you are in the right circumstance, it is definitely a big help, and a nice thing to have all the time.