[RickS]

Flexbox layouts "work like you think they work" for the most part, which is really nice, and far better than their predecessors.

The 3 "holy shit we needed this before!" features IMO are: vertical centering, height matching (if you have 3 columns in a row, and one has more text, all 3 columns will have the same bottom position), and the ability to evenly distribute objects across space.

check this out for more: https://css-tricks.com/snippets/css/a-guide-to-flexbox/

caveat: flexbox support, while passably good, is still shaky in places.

[leeoniya]

the ability to dynamically fill the remaining space is also huge.