A few of the features I like
- The lack of curly braces makes things look cleaner, especially when nesting
- The ease of using a grid framework (eg. Blueprint) while keeping the markup clean. This is made even better by setting a variable for an elements width in columns and using it to calculate the width something else needs to fill the remaining space. I'll only need to change 3 variables when I transition from the fixed width grid that I'm using to develop and the fluid grid that I'll want in production.
- Mixins for clearfix, hiding something, etc. Compass also has some built in for CSS3 things that require browser specific settings
- Nice presentation of the different styles that apply to an element between different page ids, states, and when javascript is and isn't enabled (Drupal adds a class 'js' to <html>).