Having jumped back into some green field work in Scala in the past few days, I will say I'm quite impressed with the improvements to the SBT, IntelliJ, universe. Compile time seems to be improved considerably (though the project is still quite small so time will certainly tell).

One problem, which is also one of the advantages of scala is that the interop with Java often means that all your Option[] etc code can still get NPEed by some offending Java Lib you've decided to use.

As the fidelity and ubiquity of pure scala libs improves this will hopefully go away to a some extend.