After learning sbt I've found it to be one of my favorite build tools out there. The fact that the build.sbt file is basically just a dialect of Scala allows for some very complex build jobs to be done easily.

Also the simplifications coming with sbt 1.0 like removing the Build.scala and dropping support for multiple build.sbt files makes it a bit cleaner in my mind at least. Before everything was spread around in multiple files (and possible 2 different build definition styles with the .sbt and .scala files) instead now everything is in pretty much one single file with a clean enough syntax for anyone to learn. (as someone said you only really need to know :=, += and +== of which the latter 2 function the same as they do in the standard lib for collections)

edit: Sorry was wrong about the multiple build.sbt support. Its still in but working with a single build.sbt has been made easier over the 0.13.x versions and we reverted all of our multi project builds into that and I just assumed it was being dropped (We also had a lot of Build.scala stuff so I guess i got mixed)