I rebuilt my personal site on Flexbox in December last year after making the call that it was widely supported enough [1]. There were a few hiccups:
1. Safari's requirement to use the webkit- prefix is a pain. Thankfully there are SASS libraries that work around that [2], but you aren't using Flexbox directly.
2. Google's pagespeed tools doesn't support it. It's an ancient version of Webkit -- your mobile score will suffer. If that matters to you, you'll have to do some hacking to ensure that it doesn't affect things on the mobile side.
1. Safari's requirement to use the webkit- prefix is a pain. Thankfully there are SASS libraries that work around that [2], but you aren't using Flexbox directly.
2. Google's pagespeed tools doesn't support it. It's an ancient version of Webkit -- your mobile score will suffer. If that matters to you, you'll have to do some hacking to ensure that it doesn't affect things on the mobile side.
[1] for a personal site.
[2] https://github.com/philipwalton/solved-by-flexbox