iOS 5 is compatible with iPhone 3GS, iPhone 4, iPhone 4S, iPad, iPad 2, iPod touch 3rd and 4th generation. There are over 200 new features in iOS 5. Notification Center, iMessage, Newsstand, Reminders and iCloud support are few of the main changes. However not all iOS 5 features are available on all devices capable of running iOS 5.
Siri is really not part of iOS 5 but an exclusive app for iPhone 4S. Many view it as a feature good enough to upgrade to iPhone 4S. Some has viewed it as an upgrade ‘bait’ from Apple. But insider points to Siri’s need of powerful processing, with circuitry logic found only in iPhone 4S.
AirPlay supports video mirroring of content over to HDTV via AppleTV. This feature requires iPad 2 or iPhone 4S.
Multitasking Gestures is iPad 2 only. With multitasking features, you can reveal the multitasking bar with four or five finger swipe up, pinch to return to home screen, and swipe left or right to switch between apps.
iOS 5 comes with the ability to split the virtual keyboard, useful for typing in landscape orientation. This feature is for iPad and iPad 2 only.
The new Reminders app allows you to set alert based on location. Due probably to its “battery draining” requirement for constant location tracking, this feature is available on iPhone 4 and iPhone 4S.
Safari Tabbed Browsing
Tabbed browsing in mobile Safari debuts with iOS 5, but it is only available on the iPad and iPad 2.
Safari Find On Page
Safari “Find On Page” is not new as it was introduced in iOS 4.2, ‘hidden’ under the search bar. iOS 5 brings this feature conveniently on top of the virtual keyboard. “Find On Page” is available on iPad and iPad 2.
HDR in Camera app is an iOS 4 feature. This is just to highlight that Camera HDR feature is not supported when using iPhone 3GS.