Recs.
Updated
Foundation is a highly customizable and powerful front-end framework, designed with ease of use, speed of development and flexible design in mind.
Main features include responsive layout, flexible grid, source ordering, typography, forms, buttons, navigation, media queries, jQuery & JS libraries.
Specs
Pros
Pro Uses REMs instead of pixels
Foundation uses REMs instead of pixels, meaning you don't have to state an explicit height, width, padding, etc, for every device. Simply put, using REMs means you can just state font-size: 80%; and have the whole component (and its nested elements) shrink by 20%.
This is great for making your site mobile friendly. There is also a Sass function in Zurb that converts pixels to REMs so if you're used to thinking in pixels, you don't have to learn a different system.
Pro Easy customization
Just by looking at the name, Foundation merely provides designers with a foundation of sorts on which they can build their design. It can be customized easily through SASS, a powerful CSS pre-processor or by overriding the default CSS styles.
Pro Easily extensible with a selection of add-ons
There's a variety of front-end templates, icon fonts, responsive table examples, SVG icons and stencils that help you quick-start or easily improve on your site.
Pro Uses Interchange to load responsive content
Foundation comes with Interchange, it makes use of media queries to load images responsively and create content that's suited to different browsers and devices.
Pro Good mobile support
Foundation was one of the first frameworks to adopt a mobile-first philosophy. By focusing on mobile design first, Foundation makes designers think on what kind of content is important, relevant and interesting to the users without thinking too much on the space.
Cons
Con Can be hard for beginners to grasp
Since Foundation is built to be customizable, it's default style may not be very appealing for most. While it's true that most production-ready websites shouldn't be using the default style of a css framework (they would all end up looking the same), this is even more true for Foundation.
Con Documentation is a bit better than average
Documentation could be written better and clearer, with many more example than they currently have. Sometimes hard to find solutions for detailed css problems.
Recommendations
Comments
Out of Date Pros + Cons
Pro Out of the box support for pricing tables
Foundation can transform an unordered list into a nice table. You only need to provide the proper classes.
Pro Built-in tour
Foundation comes with an easy way of creating tours out of the box.