I think that there are 2 aspects to IS that need to be conspired, first, and it was mentioned before is that IBIS has the ability to correct for rotational displacement, like what you do when you press the shutter, ILIS can't deal with rotation, so the IBIS wins because rotation will always be there in hand held situations,
BUT. What is important to realize is that image stabilization and the stops claimed are relative.
Consider film, there was a golden rule of 1/FL as a minimum shutter speed. This was to give "acceptable sharpness" on an 8x10 inch print. Acceptable sharpness is judged by the same principles as DOF with a circle of confusion of 1/100 of an inch at the print.
In film, not every one could shoot at 1/FL. It was a guide, and each person with their technique, could either do better or worse. Remember that point, IS does not give 3 (or what ever the claim is) stops over 1/FL, it gives 3 stops over what you can do.
Now lets move to digital IS and what pentax bodies can do.
The following were shot with a K7D and a Pentax SMC 300/4 plus SMC-F 1.7x AF converter. I.e. a 510mm focal length, at 1/40 of a second
For the shor, i was standing unsupported, holding the lens, not leaning against anything to either steady myself or the lens
and 100% crop of the head
Now, simple math considering focal length and crop factor says the rule of thumb should be 1/750 of a second, and that 1/40th is more than 4 stops gain.
This does not mean that Pentax offers 4 stops, what it means is that I had a very steady stance good technique, and did not rush the shot.
It is and always will be about technique