I have never tried to write Scala in Netbeans personally, but according to Dick Wall, Scala support in Netbeans is pretty much the best of the best among the 3 main IDEs (IntelliJ, Eclipse and Netbeans), I know it's just anecdotal, but it's from a fairly trusted source that literally inserted a whole new section into its Java Posse podcast so that it can search through Scala.
, . http://wiki.netbeans.org/Scala