bench.rb

require "coffee-script"
require "benchmark"

Benchmark.bmbm do |x|
  x.report("evaluate") do
    100.times { CoffeeScript.evaluate "a = 1" }
  end
end

gistfile1.txt

~/Projects/ruby-coffee-script(master)% ruby bench.rb
Rehearsal --------------------------------------------
evaluate   0.010000   0.100000  14.490000 ( 14.767549)
---------------------------------- total: 14.490000sec

               user     system      total        real
evaluate   0.010000   0.130000  14.540000 ( 14.903688)

~/Projects/ruby-coffee-script(master)% git checkout v8
Switched to branch 'v8'

~/Projects/ruby-coffee-script(v8)% ruby bench.rb  
Rehearsal --------------------------------------------
evaluate   0.290000   0.040000   0.330000 (  0.322984)
----------------------------------- total: 0.330000sec

               user     system      total        real
evaluate   0.170000   0.020000   0.190000 (  0.185008)