Five days after releasing iOS 9 to the public, Apple says that the newest version of its mobile OS is also its fastest growing.

Apple today announced that iOS 9 is “off to an amazing start” with the fastest iOS adoption ever. In less than one week, Apple says that more than 50 percent of devices are now using iOS 9.

iOS 9 adds features like an improved version of Siri that also includes Proactive Assistant, which will try to predict contacts, apps, and news that you want before you ask for them. Also included in iOS 9 is a new app switcher, a new system font, split-screen multitasking on select iPad models, and more. 

Apple also reaffirmed that the iPhone 6s and iPhone 6s Plus will launch in stores at 8:00 am local time on September 25. Apple Stores will have both models available for walk-in customers, though would-be buyers are urged to arrive early. If you’d prefer to reserve an iPhone 6s or 6s Plus online and pick it up in-store, avoiding the crowds in the process, Apple says that it’ll begin allowing online reservations from Apple.com starting September 26.