Deploying to heroku I've seen some problems when this is set to true.
For some reason, formtastic does not reload some classes when it's needed. So I see things like:
NoMethodError: undefined method `editor' for #<ActiveAdmin::Application:0x007f08134ae5f8>
ActionView::Template::Error (Unable to find input class HtmlEditorInput)
/app/config/initializers/active_admin_editor.rb:1:in `<top (required)>': uninitialized constant ActiveAdmin::Editor (NameError)
See: rails/spring#95 for references.
I was able to make a workaround for this error, prepending this to the initializer:
require 'active_admin_editor'
require "#{Gem::Specification.find_by_name("active_admin_editor").gem_dir}/app/inputs/html_editor_input"
This is problem an error more related to Formtastic than to this gem, but this should be useful for someone who has the same problem.