I'm sorry I haven't noticed. But I do have noticed http://news.ycombinator.com/item?id=1387630 because it points to the page I was posting, the homepage. Too bad it hasn't became very popular
I agree, I don't see it either. The whole point of my previous comment was to show that OS X ships with so many things that you don't have to install anything to start programming in PHP, Python or Ruby. "Until you have to compile something" refers to the fact that this claim doesn't hold anymore when you have to compile, for example, a native extension to those languages.
You don't even have to grab MAMP or Xcode, since Apache, PHP, Ruby, Python, emacs and vim come preinstalled with OS X. So you just have to get the database server. Until you have to compile something.
It depends on how aggressively you optimize. In the worst case scenario (the compiler just copies the code that the interpreter would run) you end up with the same performance as the interpreter.