Small test class I've written to support measuring the difference between using a direct index to get fields from a SqlCommand or fetching the index through GetOrdinal.
Install this database: http://msftdbprodsamples.codeplex.com/releases/view/93587 to run the project.
Full blog post can be found here: http://kristofmattei.be/2014/05/25/impact-getordinal-performance/