[asddubs]

My point is that it's not an objective measure of design quality, i.e. how well does a person who hasn't used the software before use it, or how quickly do they learn it. Whether that matters more than your existing users is up to you

[Gormo]

There are no objective measures of design quality. Every aspect of interface design can only be measured in the extent to which it facilitates the user's access to the functionality of the software, so the only metrics that apply are ones that reflect the users' subjective experience.

And that experience is determined as much by the users' own expectations and prior experiences -- yes, including habits and muscle memory -- as any quality of the interface or the design of the software.

It's not merely a matter of optimizing the new-user experience for your own particualy software, either, as new users to your software will still be bringing with them the expectations and habits they've acquired through experience with other software. We're not in the '70s anymore, with new users likely never having used any software before, and where you're starting from a clean slate. People today have lots of particular expectations of software, informed by conventions evolved over decades and their own years of experience.