The extension allows you to specify a simple pattern for generated event handler names in the WinForms designer, WebForms designer and code window. It does not currently work for the XAML designer. It also allows you to use delegate inference when adding eventhandlers instead of using explicit delegate constructors. See http://einaregilsson.com/better-eventhandler-names-in-visual-studio-2010/ for detailed information.
Despite the name of the blog post the extension now works in VS2010, VS2012, VS2013 and VS2015 :)