As expected, Apple opened the download gate for iOS 4 today shortly after 1 p.m. Eastern time, 10 a.m. Pacific time.

The mobile operating system upgrade appeared to download and install with few problems, although some users complained that backups of their iPhones were taking much longer than usual.

Downloads initiated by Computerworld staffers immediately upon the 1 p.m. Eastern time launch took approximately 19 minutes to complete, while users on Apple's iPhone support forum reported total upgrade times -- including downloading the update, backing up their iPhones and restoring them with the new operating system -- that ranged from 20 minutes to over an hour. The iOS 4 update weighed in at almost 580MB.

However, some iPhone owners encountered problems in the backup portion of the process.

"Stuck in 'back up' mode for 20 minutes so far -- no visible progress," said a user identified as "sclntx" on the Apple support forum at 2:12 p.m. Eastern time. "Arrrgggghhhh."

"It looks as though it is sitting at the backup part, even though I synced and backed up before hitting the update button," said "scsutke92" on a discussion thread dedicated to the problem.

Full story: Computerworld