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.
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.
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.