Egde works perfect. It's the IE11 that causes trouble. I use flexbox on our intranet and we have stil many people in the company who uses IE. It is always horrible to see my layout crushed on their displays.
Yeah, IE11 is the odd one out, that's why I said to not go too exotic ;) It depends on what browsers your visitors use really. If you have a high percentage of old IE users (corporate environments mostly), don't use it just yet...
Thanks for your answer. We have decided to use flexbox for small things only (like equal-height columns) and then provide a fallback for older IE versions.