[Cushman]

Ruby presents a VM; someone who understands the capabilities and limitations of that machine will be able to write Ruby code much more effectively than someone who does not, simply because they will understand what they are writing.

It would not shock me if most Rails devs were in fact Ruby tinkerers; and there's nothing wrong with that, if that's all you need to do.

[jamesbritt]

Every time I've heard people discuss that level of concern over code speed or space considerations the topic turns to C extensions. I cannot recall ever hearing or reading about tuning ruby code for its VM. Or even C code. Perhaps that's because I've never had the need to be concerned about it, but if there exists any writings or conference video on this i'd be curious to take a look.