Apple iOS 4 arrives today: What’s in store for the Apple iPhone?

The Apple’s iOS 4 arrives Monday for owners of the iPhone 3GS and third generation iPod Touch, delivering a bevy of new features worth the upgrade. If you’re not getting an iPhone 4 (by choice or limited stock availability), iOS 4 should supercharge your old iPhone with new tricks until your next upgrade.

With the impending iPhone 4 launch this Thursday, Apple will be rolling out the new iOS4 software to compatible i-devices within the next few hours. These devices include the iPhone 3GS, iPad (ipad update later this year) and iPod Touch.

iOS 4 will bring a whole host of new features with it, such as the long awaited multitasking, folder support, digital zoom for cameras and an updated email app across the board. There will be many more minor updates but these are the main ones you’ll notice and want the most!

Remember that not all previous Apple devices are capable of running the new OS, such as the original iPhone and the 1st generation iPod Touch. The iPhone 3G and 3GS will be able to handle the update, but may not receive all the new features and functionality due to hardware limitations.

Apple has not specified what time it will be releasing iOS 4, but if last year’s 3.0 release is anything to go by, expect the new operating system to hit the tubes sometime after 1 p.m. Eastern/10 a.m. Pacific Time. Patience is also a must, as millions of devices are eligible for the free upgrade, putting a lot of pressure of Apple’s servers.

Before we delve into the goodies within iOS 4, a sad reminder for original iPhone and iPod Touch users: you won’t be able to upgrade to iOS 4, as Apple says the hardware on these devices is not supported. iPhone 3G owners will get the update.

Also, if you have an iPad (which runs iOS 3.2), iOS 4 will arrive for you only in September. On the reverse, many iPad-only features by now have been ported into iOS 4 for. So here are some of the cool new and useful features in iOS 4.

As simple as it sounds, this feature was missing on the iPhone. The folders feature in iOS 4 will help you declutter your home screen, letting you compile under a single location up to 12 applications.

To access folders, enter customize mode (tap on an icon until all icons start jiggling), slide any icon on to another and a new folder is created. You can rename the folder to your liking, but iOS 4 will also suggest a folder name if applications grouped in a folder belong to the same category (like games, utilities, travel).

iOS 4 lets you set a wallpaper not only for the lock screen (as previously available), but also for the home screen. Like on the iPad, you will have the option to select a different image for the lock and home screen, or you can use the same image throughout. There is no way to set a wallpaper for each of your home screens, though.

The first thing you will notice in the Mail app in iOS 4 is the unified inbox. Users will multiple e-mail accounts have been longing for this feature for a while, and Apple finally delivered.

There is also support for threaded messages, so you can easily follow up on conversations (each discussion has a single entry that you can tap on and expand it). A big boon for business users will also be support for multiple Exchange account, as only one per device was available by now.

Alongside the predictive typing on the iPhone, spelling corrections were missing, but this issue is resolved with iOS 4. Misspelled words will be underlines with a jagged red line, and when tapped correction suggestions will be displayed. This feature works system-wide, including in Mail and Notes.