A better Scala REPL?

The Scala REPL has been often touted as an advantage for the language: an interactive, exploratory experience very different from the static, often-IDE-based experience that for many is the bulk of their experience using Scala. Nevertheless, in comparison, the Scala REPL really sucks: buggy & unfriendly, it is not a place you want to spend most of your time. What if the Scala REPL had the same autocomplete as you'd get in Eclipse or IntelliJ? What if it had syntax-highlighting for everything? What if you could load libraries like Shapeless or Akka-HTTP to try out, without needing to muck with SBT? What if your Scala REPL was as versatile, usable and configurable as Bash or Zsh, and could be used as your home on the command line? Come hear about how you could turn all these "what if"s into a reality!