Image Stabilisation systems are brilliant. Should you get it? Absolute no brainer IMHO.
Why would you not want a feature that is as good as having an instant built in tripod? You can hand hold at shutter speeds of two, three and even four stops longer than without IS. 1/60sec becomes the equivalent of 1/4sec on a tripod. How incredible is that? And there is no penalty for this, apart maybe from cost.
And sometimes there doesn't appear to be any extra cost either - if it's built in to the camera, obviously zero cost to additional lenses, and most IS/VR lenses don't appear to carry a premium either, eg Canon 17-55 2.8 IS, a superb lens by any standard, is actually cheaper than the identical spec Nikon without VR. Of course the famous Canon 70-200 zooms are much more expensive with IS, but I can't think of any others off hand, and I was happy to pay the extra for my 70-200 4 IS, and I think it is a much more useful lens, for me, than the f/2.8 non-IS lens all things considered.
Camera shake kills more sharpness than any other cause, and the extra magnification that you get with crop format digital makes long lenses even more prone to shake than they are on full frame or film cameras. There is no such thing as zero camera shake, it is only ever reduced to acceptable levels but it's always there, eating away at critical sharpness, often unnoticed as the cause of the slightly soft images we strive so hard to avoid.
The other thing about in-lens IS/VR is that it stabilises the viewfinder image whereas in-camera does not. With long lenses this makes framing moving subjects a heck of a lot easier, and it makes tighter framing easier with any subject for even more quality upsides.
I honestly think whole question is a non debate TBH.