It's incredibly difficult to find good Scala developers today, no doubt. However, it is incredibly easy to find Java developers who are curious about expanding their skillset. Those are the guys and gals who I hire, simply because it's faster for a Java dev to go through the ramp-up time on Scala than it is to wait for a pure-Scala dev to come onto the market.

Scala does not run slower than Java. Period. Additionally, the very nature of Scala and Akka allow you to be much, much more efficient on the hardware you're using; if you're writing Java code that requires, say, 100 application servers, often times you can get away with half of that if you're writing good Scala/Akka code (and because of the nature of Scala, it's much easier to write good, solid code than it is in Java).