The list of gems in the Gemfile is taken from http://www.ruby-forum.com/topic/393617. 

Other than the Gems and one model, this is an empty rails application.

With Ruby 1.9.2-p180 installed with rvm, Rails takes 20 seconds to start (measured by 'rake').  Same for ruby-1.9.2-head.

With REE 1.8.7, 'rake' runs in 7 seconds.

If you want to profile it, install the ruby-prof gem and then do:
ruby-prof `which rake` > /tmp/out
Here is my profile output for 1.9.2: http://dl.dropbox.com/u/6607107/profile.txt