Balloon engine is used for special rendering (see asBalloonCanvas), for example complex borders, it uses a plugin (B2DPlugin), has (has better) antialiasing.
I think balloon based rendering is much more importent for squeak than pharo.
(Pharo looks more flat). Take a look at older squeak releases (screenshots) to get a feel of it).
Can someone explain to me the importance of Pharo's Balloon engine ? What it offers that Athens and Morphic dont already have ? In which scenarios its worth using ? Where I can find documentation about it ?��