I feel you..... I was more wondering if there was some better compromise point between pre-allocated / dynamic but as you say, there are tradeoffs.
You're right, there must be a lot more low-hanging fruit out there. Something interesting though... isn't the Ruby interpreter just a standard (RubySpec)? JRuby (and Rubinius I think?) are other, better-performing implementations, correct? I've been thinking about trying JRuby since I was looking into Grails and thought "eh why not just try JRuby on Rails".
but i've kinda gone in the other direction anyway and am more interested in Clojure > Ruby, especially since Clojure "frameworks" are just dead simple libs. It's weird because RoR was around first (I think, maybe some overlap in development...) but it seems that now that Clojure and Scala exist, RoR is kindof like a bad compromise between the two.
Though Clojure is kindof minimal and not everyone is singing Scala's praises...