I've just dropped the ~sparc keyword on dev-ruby/rspec-rails 1.2.0 due to the new dev-ruby/rack dependency. Please feel free to keyword both >=rack-0.4.0 and rspec-rails-1.2.0.
added ~sparc to =dev-ruby/rspec-rails-1.2.2 and =dev-ruby/rack-0.9.1