I've also seen a speedup in Rails app boot time (the require optimizations):
1.9.3-p194: 11.8s
1.9.3-p385: 9.9s
2.0.0-rc2: 6.1s!
Tests were done with `time bundle exec rake environment` 5 times, dropping the highest and lowest and getting the mean of the rest (lazy snow day benchmarking). Very exciting!
Not tried 2.0 yet but got very significant speedup of 1.93 (about 3x) when I enabled optimisation in the build. Were the build settings similar for both versions in your tests?
$ ruby --version
ruby 1.9.3p385 (2013-02-06 revision 39114) [x86_64-darwin12.2.1]
$ time ruby pidigits.rb 10000 2>&1 > /dev/null
17.51s user 0.11s system 99% cpu 17.639 total
$ ruby --version
ruby 2.0.0p0 (2013-02-24 revision 39474) [x86_64-darwin12.2.1]
$ time ruby pidigits.rb 10000 2>&1 > /dev/null
4.64s user 0.27s system 99% cpu 4.927 total
That's a significant difference in speed. Going from 17.51 seconds to 4.64 seconds
1. https://gist.github.com/thoughtpolice/5025417