I kinda doesn't like the concept of such cryptic representations of standard language. May be by writing such way you saved a lot of characters, but anytime standard CSS is lot more readable thus maintainable.
Though I also feel, browser specific styles are really painful. And I also miss lack of functions, variable in CSS.
While you can write functions to create abbreviated versions of CSS properties, it's entirely optional.
Also I actually prefer Stylus' mixins and functions to SASS'.