Finally! Apple has released final version of iOS 4 previously known as iPhone OS 4.0 for iPhone iPhone 3G/3GS and iPod Touch 2G/3G. iOS 4 will no doubt be one of the major software updates by Apple, as it brings 100+ new features to your iPhone! Unfortunately, iOS 4 is not available for iPhone 2G and iPod Touch 1G, but hackers are already working on to bring iOS 4 to 1st and 2nd generation iPhone/iPod Touch, hopefully there will be a good news soon regarding this.
Updating to iTunes is pretty simple as previous firmware updates. All you need to do is to connect your iPhone/iPod Touch to your computer and start iTunes, you should see following update message on it.
A newer version of iPhone software is available (version 4.0). To update your iPhone with latest software, click Update.
Just hit the "Download and Install" button and leave rest for iTunes! You should have your iDevice on latest iOS 4 once the installation is done.
As always, we recommend people who rely on jailbreaking and unlocking to hold the update till updated tools arrive.
Official Download Links for iOS 4 (From Apple)
iOS 4 Jailbreak/Unlock Summary
Jailbreak: Apple has released iOS 4 final built/version. iPhone 3G and iPod Touch 2G users can use latest Redsn0w (0.9.5b5-3) for Windows/Mac to jailbreak iOS 4, and iPhone 3GS users can use PwnageTool Bundles to jailbreak iOS 4. GeoHot has also claimed to jailbreak OS 4.0 with Blackra1n tool, but tool hasn't arrived yet.
Unlock: As promised, after public release of iOS 4.0, Dev-Team has released Ultrasn0w 0.93 to unlock iPhone 3G/3GS running latest iOS 4 with baseband 04.26.08, 05.11.07, 05.12.01 and latest 05.13.04. Previously, Dev-Team released Ultrasn0w 0.92.1 to unlock iPhone 3G/3GS with baseband 04.26.08. iPhone 3GS users may also use Blacksn0w RC2 for unlock, but it's not an official tool and bit buggy as well.
Update 1: Download iOS 4.0.1 for iPhone 4, iPhone 3GS and iPhone 3G
Update 2: iOS 4.1 Beta 2 for iPhone 4, 3G, 3GS and iPod Touch 2G, 3G Released!
Update 3: iOS 4.1 Beta 3 for iPhone 4, 3G, 3GS and iPod Touch 2G, 3G Released!
Update 4: iOS 4.0.2 for iPhone 4, 3GS, 3G & iPod Touch 2G, 3G Released!