Very excited to see this. A couple things I saw while taking a peek:

• Reorganization of sass and script files is great. Less cumbersome to integrate into a project, and much more modular.

• The settings and overriding defaults seems easier to manage which is nice.

• Wow, they spent quite a bit of time to slim down the footprint of the css and javascript. There is some interesting stuff with auto prefixing during compilation. The goal being to remove unnecessary browser prefixes within the compiled CSS. (http://foundation.zurb.com/sites/docs/sass.html)

• They added a few new javascript utilities. The keyboard library and updated media queries library will be very useful. There is a function called onImagesLoaded(), that assists with preloading images as well, which looks useful. (http://foundation.zurb.com/sites/docs/javascript-utilities.html)

• Flexbox Grid! Wow this is going to be amazing. Even better, the majority of the syntax looks similar to the normal grid's syntax. Nonflexbox has been something we've been hacking around for a while at Authentic F&F, stoked to see this is here now.

• Doesn't seem like the forms and UI controls are too much different. We never really use those anyway, so maybe I'm just not familiar enough.

In general some really great stuff here making the framework more lightweight and modular. Very excited to start using this, hoping upgrading Foundation4/5 projects is rather straightforward.