The new version IntelliJ IDEA 2016.2 is out!
It includes a new feature to support font ligatures.
It looks very promising, so I downloaded and installed the font FiraCode.
But I noticed rough edges in the font.
I enabled the feature in
Settings → Editor → Colors & Fonts → Font and selected
FiraCode as Font.
I noticed the font looks to have rough edges as you can see in the next screenshot.
When I changed my Editor Aliasing in the settings, it looked a lot better.