Arguably the most intriguing addition to iPhone OS 4 is the support for multitasking. It comes in a variety of flavors--via push notifications, background music, VoIP, and more. We'll take you through a few of them in the following slides.
With iPhone OS 4, you'll finally be able to play streaming music from Internet radio services like Pandora while you're in other areas of the phone. Previously the only app that was allowed to play music while you were switching between apps was the iPhone's own iPod player.
Pandora from lock screen
In addition, you'll be able to control your Pandora music from the lock screen, which you couldn't do previously.
With iPhone OS 4, you can also now take calls over Skype while in other areas of the phone. We don't know yet, however, if you are able to do this via Wi-Fi only or with 3G as well.
An example of the Skype app with multitasking.
GPS in the background
Similarly, you can now run the TomTom GPS app in the background while you're taking a phone call.
iPhone OS 4 lets you choose which location apps you want to run in the background. So you don't have to let all of them run in the background if you don't want to.
Another welcome addition to iPhone OS 4 are improvements to the Mail app. You will now get a unified in-box, multiple Exchange accounts, fast in-box switching, threaded conversations, and the capability to open attachments with apps.
You can organize your e-mail by thread with iPhone OS 4.
Apple clearly recognizes the popularity of gaming among iPhone users, and introduced a social gaming platform. There will be a gaming leaderboard with achievements, matchmaking, and more.
Finally, Apple iPhone OS 4 will introduce a folder infrastructure so you can easily organize your apps and documents.
Example of Folders
An example of how Folders would work. You can add apps by dragging and dropping them.
Unsurprisingly, Apple iPhone OS 4 takes a cue from the iPad when it comes to iBooks integration. You will now be able to purchase and download ebooks from the iBooks store and read them on the iPhone as well. You can sync pages and bookmarks, too.
Apple will also add Cisco and Juniper VPN services to iPhone OS 4, plus support for Exchange 2010.
Apple iPhone OS 4 will also make it easier for app developers to integrate ads into their apps.
Example of iAd
This is an example of an iAd implementation in an app.
Many more iPhone OS 4 updates
There are many more iPhone OS 4 updates in the works, according to Steve Jobs. One of them is the capability to use Bluetooth keyboards.