The flex box model, aka Flexbox, will make designing layouts in CSS and HTML a lot easier once it hits mainstream. How close is it to being widely supported? It's actually not too bad, with global support at 88.88% as of 3/2/15. The main issue is with versions of Internet Explorer earlier than 10. Modern Chrome and Firefox, as well as mobile browsers almost all support Flexbox. Since this is a new tool that will likely be employed in CSS frameworks of the future, it's useful to know how and why it will happen. Here are a few good links.
Gets into the nitty-gritty of Flexbox and has some examples. Not the best page for figuring out good use cases quickly, but worth looking at.
Great examples of how to use Flexbox and the various scenarios where it makes things a lot easier. This clarifies why it will be a standard in the coming years.
But can we really use it today? I'd say if you're designing a mobile app in HTML or don't care about backwards compatability on your site: go ahead. For the normal front end web folks... you're going to want to give it a year and check back.