[rasmusfabbe]

Thanks for the thoughtful comment. Indeed really small sizes like 11px, distinguishing factors are few and even San Francisco and Roboto start looking like the same font, at least as far as most people are concerned. The goal with Interface is not to create a unique-looking typeface, or even to try to make something different in terms of style, but to create the best possible small-size, computer-screen, user-interface oriented font, even if that means that some characteristics become very similar to other typefaces. For instance.

[jack_jennings]

My argument is only that starting with the proportion and metrics of Roboto and not changing them means that what you will end up with at best is a marginal improvment over Roboto. If "marinal improvement over Roboto" is what you are aiming for, great, but don't oversell it or your work will be dismissed in the same way that I did in the original post. There are myriad solutions to how letterforms are created, and it isn't a foregone conclusion that these forms are or will continue to be "the best".