Switching between languages based on context is good; you might have a favorite pet language for desktop work, embedded work, iPhone work, and web work.  But splitting your brain cells between languages for the same sort of task, in the case web development, isn't very efficient.<p>I have to do it, for different platforms, but that means I'm constantly switching between design techniques and I can't reuse one body of common code.<p>It just makes sense to put all your eggs in one basket and make the switch.  However, it's important to have a healthy respect for other languages and their pros and cons compared to your own choice.