While these things are always hard to quantify, it seems that the amount of complaints coming in from the web is more than typical for an Apple release.

One of the most common issues appears to be this error saying that the phone could not be restored after the upgrade was installed. In other words, this error results in a bricked iPhone, requiring a lengthy restore process to fix.

One Twitter user, @michaelterren, said that he set his phone for an overnight update, but woke up to find his phone had been wiped.

Another said they had some teething problems with the new iCloud service, but eventually got it to work after a few tries.

These problems seem to be more widespread than just a handful of people, if the #ios5 Twitter hashtag is anything to go by.

Gizmodo has also run a poll on the issue, with most users at time of writing saying their install experience was 'Terrible'.

And then there are the users who simply have to wait a while for their update to finish.

But for those who emerge unscathed, iOS 5 is indeed a worthy update, with cloud storage, wireless sync, centralised notifications, and a slick Apple-to-Apple texting service headlining the feature list.

For those hanging out for the iOS virtual assistant, though, you'll have to wait until tomorrow for the iPhone 4s, the only handset to feature the software.

iOS 5 is available for the iPhone 3Gs and 4, iPod Touch 3 and 4, and the iPad 1 and 2.