Which grid framework should I use?

As I’m starting out trying to create a web application with Rails, being new to both Rails and web development, I’m trying to figure out how to best compose its layout. So far I’ve been tipped about the Blueprint framework. Just as I was learning Blueprint however, I discovered a Sass-based framework: Susy ( http://susy.oddbird.net/). As I like the Haml language a lot (so far), I definitely see the appeal of a Sass-based framework.

What’s the popular option among experienced Rails developers these days? Is Susy often used?