The iOS 7 has redesigned user interface and various new features like Control Center, Notification Center, improved Multitasking, AirDrop, enhanced Photos, Safari, Siri and new iTunes Radio.
iOS 7 will be available only for the iPhone 4, iPhone 4S, iPhone 5, iPod touch 5th generation, iPad 2, iPad with retina display (third and fourth generations) and the iPad Mini.
OS X Mavericks comes with more than 200 new features. It brings new Maps, iBooks, Finder Tabs and Tags, Enhanced multiple display support, Notifications, Performance and energy saving's, and Updated Safari browser.
Here the download links for the developers beta versions of iOS7 and OS X Mavericks from Dev Center