The Readability app has been updated with iOS 8, iPhone 6, and iPhone 6 Plus support, along with a new share extension, and pixel perfect typography adjustments.
The MLB.com At Bat app has been updated with numerous improvements including a redesigned news reader, support for the iPhone 6 and iPhone 6 Plus, improved team schedule navigation, and more.
After updating its iPad app, Skype released a similar update for its iPhone app, bringing HD Video calls to the iPhone 5 as well as improved call quality and stability
The Amazon app has been updated to let you see more content on the larger displays of the iPhone 6 and iPhone 6 Plus. It's also gained the ability to search with your voice.
The Yelp app has received a new Directions buttons which tells you how long it will take to walk or drive to a business and been optimized for the iPhone 6 and iPhone 6 Plus.
Piper Jaffray's Gene Munster published results of his team's iPhone 5s/5c launch day survey which found that 90% of buyers were upgrading their existing device.