Of course. there are lots of minor issues and surprising results with flexbox in modern IE and Firefox once you use it in more advanced ways. See
https://github.com/philipwalton/flexbugs for an overview.
Nevertheless I use flexbox almost everywhere. It's a great system to arrange anything from general layout to smaller components. There's absolutely no way that I'll deal with any kind of hacks to get basic things like vertical centering right.
