I used LESS a lot. These days I decided to try SASS and to be honest it's a better choice for CSS preprocessor. It just gives me more functionalities and better control on my code. There are few instruments for architecting your CSS logic - @mixin, @extend and placeholders. However there are differences between them and specific use cases.
I'm currently working on OrganicCSS - a micro framework based on atomic CSS concept. I'm thinking a lot for name conventions, classes and of course mixins. I decided to combine three mixins in a file called _box-model.scss. They will provide a shortcuts for margin, padding and border properties.
I really like SASS and I use it a lot in my daily job. There are tons of useful features. However there are some things which I want to do, but I can't. There are limitation in the syntax and missing functionalities. Sharing what I found, I want to know if you meet those limitation and how you get around them.
The mixins in SASS are really helpful. Here is something really short which I just start using. It's a mixin which I apply on the grid's container.