If you think your 7d is "soft", please read this.

The 1/focal length rule is perhaps one of the most misunderstood rules out there. As you say it developed during the time of full frame (film and slide). But if you went to photo school you were taught - 1/ two times focal length - for sharpness, hence a 100mm lens wasn't shot at 1/100th, but 1/200th.

But now lets enter the era of crop sensors, using the ubiquitous 100mm lens with a Canon crop of our 100mm lens becomes 160mm lens "effectively." So the rule would then have it - at 1/focal length - 1/160th; but if you are a subscriber of the 1/two times focal length, you shutter speed would be 1/320th.

If I have a lens with IS and I'm shooting on the fly (quickly) I'll use the rule of 1/focal length, so 1/160th (closest shutter speed) to ensure sharpness.

This rule applies is the subject matter doesn't require faster shutter speeds, like BIF's.

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"Photography is, indeed, an inclusive language."
Ansel Adams