[jhferris3]

Other fb employee here.

One of the other annoyances we had (I think its addressed in the note?) is that until now the interpreter (on our dev machines) and the compiler (hphpc in production) occasionally differ in small, occasionally painful ways. Unifying our development and production environments will eliminate another potential source of bugs.

Also: Tight loops don't imply a lack of understanding. Often times when you're trying to get the CSS on a page just right (across all browsers) it requires quick iteration, even if you do understand CSS well.