As anticipated, Apple has officially released iOS 4.0.1 to counter iPhone 4 signal reception issues. iOS 4.0.1 is fully compatible with iPhone 4, iPhone 3GS and with limited functionality on iPhone 3G. iOS 4.0.1 has been released to fix for iPhone 4 signals issue only. Apple has calibrated the formula to calculate the display bars showing signal reception strength.
As per some critics, this is just a software deception from Apple to disguise iPhone 4 signal reception issue, the signal strength bars might not drop suddenly but the calls would still continue to drop.
Updating iOS 4.0.1 via iTunes is pretty straight forward. All you need to do is to connect your iPhone to your computer and start iTunes, you should see an iOS 4.0.1 update message for your iPhone.
Just hit the "Download and Install" button and leave rest for iTunes! You should have your iPhone 4/3GS/3G on latest iOS 4 once the installation is done.
1. As always, we recommend users who rely on jailbreaking and unlocking to stay away for updates till further updates.
2. You should save your SHSH Blobs for iOS 4, it's necessary in case you need to downgrade your iPhone firmware from iOS 4.0.1 to iOS 4. Refer here for more details.
Official Download Links for iOS 4.0.1 (From Apple)
Update 1: Jailbreak iOS 4.0.1 on iPhone 3G with Redsn0w 0.9.5b5-5
Update 2: Unlock iOS 4.0.1 on iPhone 3G with Ultrasn0w 0.93
Update 3: iOS 4.1 Beta 2 for iPhone 4, 3G, 3GS and iPod Touch 2G, 3G Released!
Update 4: iOS 4.1 Beta 3 for iPhone 4, 3G, 3GS and iPod Touch 2G, 3G Released!
Update 5: iOS 4.0.2 for iPhone 4, 3GS, 3G & iPod Touch 2G, 3G Released!