Since Apple released iOS 7, everybody wants to hands-on the new experience as it is a major redesign from iOS6 to iOS7, as Tim Cook said "This is the biggest change since the launch of iPhone".
The UI is flatter now and new features are also introduced like Notification sync, iTunes Radio, Control Center, Notification Center etc. Jony Ive has done tremendous job in making the phone interface look simpler and effective, making it maintain the old traditional fashion of rounded icons and the framework that previous versions of iOS had.
iOS7 is still in beta, and Apple announced in WWDC that the updates will be coming this fall, but iOS developers can access the developer preview. As some of the sources said, that iOS 7 is still needed to be worked on. But most of them installed it flawlessly without any problems and are running it finely.
iOS7 is yet to make its move to iPad and iPad Mini as Apple would be wanting to roll out updates on iPhones first, but updates will be soon.
The developer preview of iOS7 is available for developers only, and those who are registered at Apple Devs can get the build for testing purposes, otherwise you need to have UDID to install iOS7 on your device.
With a simple workaround, you can install iOS7 on your iPhone without developer access or UDID, following the video tutorial below.
Tutorial
Note that you need to have the latest version, that it iOS 6.1.4 on your iPhone. If you are not, you can update automatically from the Software Updates.
Download iOS7 from below and save it on your computer. Open up iTunes and make sure you have your iPhone connected to you Desktop via USB cable. In iTunes, you need to restore the phone with the iOS 6.1.4 first and setup your phone until you get to the homescreen, and after that you have restore your phone with the iOS7 firmware you just downloaded. Wait for it till it finishes the update and it will restart.
This is a normal update and you will be able to update OTA updates for future releases, and you will be able to make calls, messages and everything. It is fully functional iOS7 on your iPhone now.
Download iOS7 Firmware