Supported Devices:

iPhone:
iPhone 3G
iPhone 3GS
iPhone 4

iPod  Touch:
iPod Touch 2nd Generation
iPod Touch 3rd Generation
iPod Touch 4th Generation

iPad:
iPad 1st Generation
iPad 2

Initial Release: 4.0 (June 21 2010)
Latest Release: 4.3.5 (July 25 2011)

New Features:
- Wallpaper on Homescreen (for iPhone and iPod Touch, not supported on iPhone 3G and iPod Touch 2nd Generation)
- Retina Display Support
- Updated icons
- Facetime
- Folders
- Game Center
- Battery Percentage (not supported on iPhone 3G and iPod Touch 2nd Generation)
- Redesigned dock (for iPhone)
-  Updated icons
- Brighter colours throughout the OS