Back in December, we invited you to try out a faster, more powerful version of Google Sheets (http://goo.gl/qvi5dP). Over the next few weeks, everyone on Rapid Release domains will automatically be upgraded to the new spreadsheet experience. Look for additional features like multiple cell selection, easier hyperlinking, and Add-ons (http://goo.gl/9MqNua) to name a few.
The new Sheets will be rolled out to Scheduled Release domains in the next 4-6 weeks. Stay tuned in the upcoming months for details about upgrading existing spreadsheets to the new Sheets.