The problem might be the difference in your keyboard settings instead of Vim. Try changing the Key Repeat setting in OS X' keyboard settings and see what happens. On my MacBook this setting affects the cursor movement speed when holding h
, j
, k
or l
.
As mentioned in comments some software such as KeyRemap4Macbook can override the system settings.
Also consider using commands ^U
, ^D
and G
instead of hjkl
when navigating around longer files.