Superficial nit: this page is <i>not</i> a good example of SIFR text replacement. It'd actually look better with a standard font stack, even if it didn't fill my screen with ClickToFlash boxes.
Wow. MacRuby sure looks awesome. I've always used Python for most of my scripting needs, but it's impossible to ignore the kind of work the MacRuby guys have done. No GIL, GCD, JIT ... fun :)