I recently started using CGI::Builder having previously used CGI::Application. CGI::Builder provides an excellent integration with session, template and user authentication modules. It has extremely thorough documentation and the examples are clear and understandable. The mailing-list has been extremely helpful with all queries.
CGI::Builder::Magic has opened my eyes to Template::Magic. My previous templating system had been Template::HTML - all good but what I really want is easy access to run-time variables from a static context! CGI::Builder/Template::Magic provide this!