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.

Font Settings

I noticed the font looks to have rough edges as you can see in the next screenshot.

Rough edges

When I changed my Editor Aliasing in the settings, it looked a lot better.

Settings Good-edge