Apple has finally released iOS 4 – its eagerly awaited next generation iOS.

Apple had given us a sneak peak of its next generation iPhone OS in April.

iOS 4 includes over 100 new features for iPhone users such as multitasking, folders, better mail app etc and more than 1500 new APIs for app developers. 

So let's take Apple's new iOS 4 for a spin to explore the new features.

iOS 4 is now available as a free upgrade to iPhone 4, iPhone 3GS, iPhone 3G, second and third generation iPod Touch users.

Here is the long list of new features in iOS 4:

Multitasking:

iPhone users will finally be able to run iPhone apps in the background. To achieve this Apple is offering developers seven multitasking services, which will allow their iPhone app to run in the background while preserving performance and battery life. We’ve started seeing multitasking enabled iPhone Apps available On The App Store since last week.

Unfortunately, the multitasking feature is available only to iPhone 4, iPhone 3GS and the third-generation iPod Touch (32GB and 64GB models from late 2009) users.

Folders:

Users can organize iPhone apps on their iPhone home screen into folders. Users can also drag and drop apps into folders.

This means iPhone users will be able to install 2160 apps instead of the current limit of 180 iPhone apps.

When any of the apps inside a folder receives an alert, you'll be informed of the same with an exclamation point over the main folder icon.

However, nothing describes this feature better than the video below. The video also gives a demo of the multitasking feature, which shows how you can close apps running in the background.

Better Mail app:

You will now be able to see messages from multiple email accounts in a unified inbox.

You can organize emails by thread in the Mail app just like in Gmail. Email threading option can be turned on or off via Settings -> Mail, Contacts, Calendar and turn on or off the 'Organize By Thread' toggle (this feature was demoed during the iPhone OS 4 event, the screenshot shows you how it can be enabled).

Customize Homescreen Wallpaper:

Users can customize the wallpaper on their iPhone homescreen in iPhone OS 4.0 (screenshot below). You can change it by going to Settings -> Wallpaper. You will now get an option to select "Set Home Screen" in addition to "Set Lock Screen" when you select an image as the wallpaper.

This feature is strangely only available to iPhone 3GS and new iPhone 4 users.

iBooks:

iBooks app for iPhone and iPod Touch is available on the App Store so you can browse, buy, and read ebooks. It also includes support for PDF.

New Enterprise features:

iOS 4.0 also brings new enterprise features such as data protection, wireless app distribution, mobile device management, SSL VPN support, allows users to set up multiple Exchange ActiveSync accounts and will also work with Exchange Server 2010.

Cellular Data Toggling:

You have an option to toggle cellular data on or off (Settings -> Network -> Cellular Data).

Messages Character Count:

You can turn on the 'Character Count' option in Messages Settings in order to keep a tab on the number of characters while typing a message (Settings -> Messages -> Character Count).

Text Messages Search:

iOS 4 extends the iPhone's inbox search feature to text messages. You can finally search through your SMS messages.

Camera Zooming:

Users taking a picture from their iPhone will now see a sliding bar at the bottom of the screen to zoom in and out while taking a picture (up to 5x digital zoom). Tap on the screen to enable the controls to use the new digital zoom feature. Alternately, tapping on the screen will also allow users to zoom in and out while taking a picture.

Web and Wikipedia Search:

As we had reported earlier, the global search screen on the iPhone now has two additional options – 'Search Web' and 'Search Wikipedia' to let users directly search for content on the web and Wikipedia.

Document Border:

Previewing documents on the iPhone will now display these files without the borders. This is expected to help squeeze in an additional pixel or two of content.

Add New Contacts:

The Contact window on the iPhone looks more streamlined in iOS 4 allowing users to enter more details about the contact without navigating away from the main screen.

iPhoto Syncing:

iPhoto users can sync their photos to the iPhone via Events, Faces and Places. 

Lyrics Data Toggling:

A new global toggling option gives you the ability to turn the display of lyrics on or off (Settings -> iPod -> Lyrics & Podcast Info).

Photo Resize Option:

Users sending large-size image files via email can choose to resize the photo on the go by selecting from the four different file size options.

Create and Edit Playlist:

The on-the-go playlists are replaced by the 'Add Playlist' option in iOS 4 that will be automatically synced back to the users' iTunes account. You will also be able to edit the playlist on the iPhone.

Album Info:

Browsing albums have traditionally displayed the tracks and the shuffle option. You can view the album thumbnail, track count, length of tracks and album release date.

Location Services For Apps:

You can enable or disable location services for each location based apps via Settings -> Location Services. Also, you also get visibility on the apps that have most recently accessed this information using the compass arrow icon.

Longer Passcodes:

Passcodes are no longer limited to just 4 numbers. You can select turn off Simple Passcode option to set a longer Passcode lock (Settings -> General -> Passcode Lock -> Simple Passcode).You can set a more secure alphanumeric and longer passcode for your iPhone. You can currently use the iPhone Configuration utility to achieve this.

iPhone Tethering:

AT&T has also announced that it will finally allow iPhone tethering with the release of iOS 4. AT&T customers will have to pay $20 to enable it. But they will need to opt for DataPro plan to be able to enable it. Its not available if you decide to stick on to unlimited data plans or choose the DataPlus plan. You can check this article for more details about AT&T’s new data plans.

New APIs, iAd, Game Centre:

iOS 4.0 includes more than 1500 new APIs for app developers.

Apple has also launched iAd, mobile advertising platform for iPhone apps.

Apple has also announced that it plans to launch Game Center, the social gaming network later this year and has provided GameKit APIs in iOS 4.0 to develop for Game Center.

Other new features:

Here some of the new features that we discovered from iOS 4 release notes:

• Calendar invitations can be sent and accepted wirelessly with supported CalDAV servers

• Support for MobileMe calendar sharing

• Suggestions and recent searches appear during a web search

• Support for Bluetooth keyboards for iPhone 3GS and iPhone 4 users

• iPod out to navigate music, podcasts and audiobooks through an iPod interface with compatible cars

• Support for iTunes gifting of apps

• Wireless notes syncing with IMAP-based mail accounts

• Persistent WiFi connection to receive push notifications for iPhone 3GS and iPhone 4 users

• Visual Voicemail messages can be kept locally even if they have been deleted from the server

• Control to lock portrait orientation for iPhone 3GS and iPhone 4 users (extension of multitasking feature)

• Audio playback controls for iPod and third-party audio apps for iPhone 3GS and iPhone 4 users (extension of multitasking feature)

• New languages, dictionaries and keyboards

• Accessibility enhancements for iPhone 3GS and iPhone 4 users

• Bluetooth improvements

• Better data protection using the device passcode as an encryption key. But this will require you to do a full restore

• Support for third-party Mobile Device Management solutions

• Support for Juniper Junos Pulse and Cisco AnyConnect SSL VPN apps (available from the App Store)

• You now have an option to also select Bing as the default search engine in Safari in addition to Google and Yahoo (Settings -> Safari -> Search Engine). 

If you’ve discovered a new feature in iOS 4 that hasn’t been mentioned here then please tell us about it in the comments.

Our Verdict

We really like the update, especially if you’re an iPhone 3GS, iPhone 4 or third-generation iPod Touch user and have access to all the new features. Features like multitasking, folders were some of the most requested features but the manner in which Apple has implemented them is quite brilliant.

We believe the combination of Apple’s new iPhone 4 and iOS 4 will be very difficult to beat.

Please do drop us in a line in the comments to tell us what you think about iOS 4 and don’t forget to tell us your favorites features.