To be honest, I found this to be an unfortunate example, especially when mentioned in the same paragraph as writing tests. Knowing all the shortcuts in VIM -- in fact, using VIM at all -- has very little impact in software productivity and quality. Remember, how efficiently a single programmer types matters very little, because that's not where most time in software development is spent, or where most problems arise, for that matter.
Again, does it matter how fast you edit when compared to spotting what to edit, which change to make, and how to explain it to your teammates? I think it matters very little. Obviously, if you're so slow you it drives your teammates crazy then it becomes a problem, but really, I don't think the difference lies in learning VIM's shortcuts.
