[timclark]

Plain old Java compiles way faster than Scala I don't believe the JVM is the main contributor to the slowdown.

Scala compilation is complex, partly due to its extremely sophisticated type system, it is also quite resource intensive - I have got the type checker to run out of memory on multiple occasions I have never seen a Java compilation fail due to lack of memory. fsc and incremental compilation do speed things up but it is still slower than compiling an equivalent amount of Java.