iPhone OS 4 Developer Preview brings multitasking, folders and more to the iPhone

It’s been 10 long months since Apple released iPhone OS 3, which brought Copy/Paste, MMS, Tether, and Spotlight to the iPhone. Today Apple is announcing the Developer Preview, which will open up all sorts of new avenues for the iPhone with seven main features with multitasking being the crowd pleaser. But there’s so much more, too: folders, unified mail accounts, iBooks, GameCenter, and more.

iPhone OS 4 is bringing home screen wallpaper, Bluetooth keyboard support, 5x digital zoom, spell check (!!!), iPod out, and more.

The OS is getting an official release this summer but will be available to developers starting today.

All this can be enjoyed simultaneously without killing the battery thanks to the new API’s efficiency, which eliminates Apple’s long-time stance that multitasking would kill batter life. Mulitasking is used with a new interface that’s actually different from other mobile platforms. It’s like a ghosting / transparent effect.

Not everything can multitask, however. Apple is only providing seven services that can take advantage of this: background audio streaming, Voice over IP apps like Skype, background location, push and local notifications task completion, and fast app switching.

Pandora and such can now be streaming audio non-stop and users can now navigate away from Skype while still being able to receive calls. This also applies to navigation apps, which means you can receive calls and do everything else without killing the TomTom app. Social networking apps, however, while able to take advantage of this new service will drop the GPS while in the background and instead run off of the cell-based A-GPS system.

iPhone OS 4 also brings a new sort of notification to the iPhone. It resides on the phone itself rather than using data servers.

With task completion, the iPhone will be able to, say, continually upload pics to Flickr while the user is doing something else.

Apple is finally bring a bit more organization to the iPhone with folders, too. Drag and drop apps on each other to automatically create a folder. The name auto completes, but it can be edited right there. Amazing function and amazing it took so long to hit the phone.

Multiple email accounts will soon be consolidated into one unified folder. Perfect for most us that hate juggling all the different mail folders.

iBooks. Big surprise here. iBooks will soon be on the iPhone (and iPod touch probably) and it takes some pages out of the Kindle’s playbook with the buy-once, read-everywhere mantra along with bookmark and sync. iBooks will soon be a major ebook force.

GameCenter is building on the already vast library of gaming apps available in the App Store. Think of it as an Xbox Live for the iPhone: leaderboards, automatic matchmaking, and achievements.