Knowing 'X'

John S's thoughts on the new hardness tester reminds me of an instrument we have in our lab: a texture analyzer.  The texture analyzer attempts to quantify the performance of a variety of materials, often in their use state.  For foods, texture analysis becomes useful when paired with sensory analysis.  The sensory analysis (performed by customers or trained panelists) describe the performance of the product, while the texture analysis puts a number on the performance.  As John mentions, comparing '2x' to 'x' is useful, but knowing what 'x' means is another matter.
Back in my selling days, we often used the x:2x comparison to get in the door to see a new industrial customer.  The standard pitch was "give me a good sample and a bad sample and a description of the problem, we'll test the product, and see if we can identify the problem rheologically.  Then, you'll have a quantitative description of the problem and can find the appropriate solution, such as a new ingredient, different process, etc."
It's my impression that a lot of industrial rheology works this way.  One runs a comparison to an internal standard; but, because of time pressures, 'x' may not need to be understood, as long as the product is working for the customer.