Recently Microsoft announced it will be discontinuing security and stability patches for IE10 and below this month. This is fantastic news and means that quite possibly the most desirous of CSS features, Flexbox, is now supported by all major browsers!
Flexbox is a W3C standard that provides a toolset for layout and alignment that better matches how most people prefer to architect their user interfaces with CSS. Some things that were previously surprisingly difficult, like vertical alignment, have become much easier and more stable. Responsive grid layouts in particular will now require much less tooling in order to achieve good results.
My recommendation is to begin preferring Flexbox for layout in all new projects moving forward.