'sbt console' compiles before it launches a repl because it includes your project's classpath. If you want a Scala repl that doesn't have your project's classpath (and hence doesn't need to compile things) start a repl separately from sbt.
Alternately, use "console-quick", which brings up a console with your dependencies on the classpath, but not your actual code.
As a (lengthy) side-note, that name really bugs me. In sbt, we have console-quick and console-project (brings up a console with your build on the classpath). Argh! These are kinds of consoles. They should be quick-console and project-console! Alas, those are the names that Mark Harrah gave us, so they're the ones we have to live with, I guess.
