In terms of gain, I see little or no gain by using this 'autoboxing' (sounds like the M25 in rush hour!:)

I like OO, but I see no benefit (and considerable overhead) in hiding the standard apis behind pseudo-OO syntax. If it came built-in that way, that's fine, but adding two layers of overhead just to achieve a different syntax doesn't ring my bells at all.

I'm not sure how to clean up the Schwartzian Transform with this code...

Perhaps the obvious, though somewhat controversial method of avoiding the code strings would be to use a prototype and pass code blocks. It would save several evals. Even so, the code will run about 4 times slower than coding the ST in the standard way, and given that the vast majority of the syntax has now become parameters to a sub (whether as strings or anon. code blocks), where is the benefit?