Just wanted to let you know of an issue I had...
Ruby 1.8.7 threw a "uninitialized constant Rails::Rack::Offline" in lib/rack-offline.rb:4
Apparently this works in ruby 1.9, but I wasn't able to test it myself.
Changing line four to " class Offline < ::Rack::Offline" fixed the issue.
Here's my fix... http://github.com/blaines/rack-offline/commit/6943251b51166ba010d30cebafe6f29b1ebe422f