Not really a bug/error but a feature request...

The chapter starts with the following code:

import scala.swing._

which indicates that swing is part of the standard Scala installation. 
Even thought it's part of the core api, I had to hunt down the
dependencies in order to be able to import the library.  The following
line needed to be added to my build.sbt file:

libraryDependencies += "org.scala-lang" % "scala-swing" % "2.11.0-M7"

It would be helpful to give an indication in the book that the user is
responsible for tracking down this dependency.

'SimpleGuiApplication' is deprecated.
For a book with the newest changes, this example should better use
'SimpleSwingApplication'.