Ever been stuck in sbt hell? Where one project requires sbt 0.10.0 and another requires 0.12.1?
Having to install multiple versions of sbt and switching back and forth between them is no fun. It's even less fun when the version of sbt you have installed seems to work, but you get baffling missing dependency issues for plugins and libraries for certain projects.
Enter sbt-extras by paulp.
This nifty little drop-in replacement for sbt is smart enough to download and cache the correct version of sbt and scala for each project. Download and drop it in your path and you'll never need to manually install a particular version of sbt again.
I honesty don't know why this is not the default version of sbt.