On the other hand, there's no canonical swing-based REPL yet, most seem to favour shelling out to Scala then wrapping the input/output streams.
It shouldn't actually be too difficult, but it would need scala.swing.text.* - which hasn't yet been ported! I do intend to revisit this little gem at some point. Alternatively we could see if it gets accepted for GSoC, I believe there was a proposal submitted to improve scala.swing.