Ditch Array.prototype methods in favor of fast array helpers

Faster, and makes the code nicer, imho.  This is a precursor to handling Arguments objects in when/function et. al., as reported by @phated via IRC.
I've heard that, but I've been using this approach in another project for quite some time now (in chrome and node 0.10.32 and 0.11.13/14), with no problems.  How does the unhappiness manifest itself?