Multitaskingâ€” this functionality is handled with a simple task switcher. You just need to double click the home button to get a list of running apps. All you need to do is select and switch.
Foldersâ€” iPhone OS 4 lets you keep all your apps in a neat folder structure. This makes it more convenient.
Unified inboxâ€” with iPhone OS 4, users will finally get a single inbox view across multiple accounts.
iBooksâ€” iBooks will wirelessly synchronize the current page and bookmarks to the cloud so that users can continue from their previous state, no matter which device they are using.
Enterprise featuresâ€”in iPhone OS 4, Apple introduces email (and attachment) encryption, mobile device management, wireless app distribution (allowing companies to distribute custom applications without needing iTunes), multiple Exchange accounts and support for Exchange 2010.
Game Centerâ€”Game Center is Apple’s take on a social gaming network. Game Center will provide a familiar set of services, like a friends list, game invitations, automatic matchmaking, leaderboards, and even achievements.
iAdâ€” iAd helps developers who create free apps targeted at mobile advertising. According to the company, iAd will help developers monetize free apps with in-app advertising that is both interactive and useful.
One negative aspect of iPhone OS 4 is its compatibility issue. While this upgrade will be made available to all users of modern iPhone and iPod touch versions, the complete system functionality will be available in only the high end versions.