Mashable is one of favorite examples of WordPress users, but recently Mashable the Internet news blog has been migrated from WordPress to custom technology stack, the Ruby on Rails for the back-end, Handlebars JS and Backbone JS for the front-end.
Below the statement from their Chief Architect if Mashable is not using WordPress anymore:
Mashable is now running on a custom technology stack. The public-facing bits are a Ruby on Rails backend, with a lot of the templating work pushed to the front-end with Handlebars and Backbone. We'll be doing a full writeup on the build in the near future.
And already made an announcement to its users about their new look
After two weeks of beta testing, we're excited to launch an all-new version of the site that delivers a better experience on every device -- from phones to tablets to desktops and beyond.
Read more Mashable new look