It's just his opinion.

Learning new languages teaches you what you know and most importantly don't know. Coming from a Java working background, I find Ruby on Rails pleasantly abstruse and remarkably concise (which makes it hard to learn, coming from the land of boilerplateness).

I have a long commute on the train and I find that when I am trying to debug/learn - (learning Ruby on Rails) - the time flies by like that. If that isn't a benefit (making time fly by when you're having fun learning), I don't know what is.