Apple has released its iOS 4 operating system software for the iPhone 3GS, iPhone 3G and iPod Touch.
The move comes ahead of the 24 June launch of its new iPhone 4 device, which comes pre-installed with the new OS.
The new operating software, which became available at 7:00pm British time yesterday, adds a number of new features to the Apple devices, including more sophisticated folder support, a new iBooks app and the iWorks productivity suite.
Users downloading the software complained of problems during the update, some reporting that the back-up process alone took between 20 minutes and an hour to complete.
Network World reports that even though the 580MB update took 19 minutes to download, the back-up process for the iPhone and updating the device with the new software was significantly longer.
Apple users vented their frustration on Apple's support forum, flooding it with complaints.
One user, “scsutke92”, wrote: “It looks as though it is sitting at the backup part, even though I synced and backed up before hitting the update button.”