I will stick with your "@" format. :)
@helgatheviking- I keep hearing about SASS and how once people use it, they love it. I decided to convert one CSS file to try it out and I don't think I will go back. I picked SASS because people say it is the more robust than LESS (more options) and heard more "bad ass" front-end devs mentioning SASS, so I ran with that.
What I like most, less coding for CSS, nested structure for visual effect and it compiles in different formats so if someone doesn't know SCSS syntax, or doesn't want to use it, they can just use the compiled CSS. You can go back to using @imports in CSS since SASS will compile them all into one style sheet (modular approach, but done right). Also the output of the CSS can be changed to Normal, Nested (looks fancy), All on One Line, or Compressed, obviously you can just spit out compressed CSS for production which is easy since it is done for you on save.
You can leave comments with "\\" like PHP for internal comments that won't display in the CSS files, so you can go wild with commenting code which in a big project would be a killer feature.
Basically you already know SASS for the most part, it is just a little modification to the way you write the CSS structure.
Compass is a little different, it is a companion add on to SASS and adds a bunch of functionality for CSS3 and some crazier things I don't know yet, but at the least with it you won't have to do vendor prefixes ever again.
I would suggest just converting a CSS file you are really familiar with (makes it a easier) to SASS only (forget Compass for now) and by the time you are done, you will like it too. ;P