To be fair, you're very unlikely to ever have to solve the kinds of scaling problems Twitter has had to solve. You'll get your app off the ground faster with Python or Ruby.
Like he states at the end of the video, when describing the 7000+ tpm during the WWC:
"...we do things like Forex spikes upon our standard baseline growth. So right now the JVM is really the only mechanism that we can build upon that gives us the flexibility to do something like that."