Tonight the iOS 5.0.1 update arrived, which means a chance to test the new over-the-air update system introduced in iOS 5. Over-the-air updates are one of the most important sanity-saving features of iOS 5 for people managing large installs of iOS devices. Instead of having to connect to iTunes, download a 700MB+ restore image and connect your iPads one by one, you can install the update directly on the device.
Here are some observations on the process.
Firstly, there's a big win in the fact that the OTA update is also a delta update - meaning that only the changes from the previous version are downloaded, not the whole operating system. Where iOS 5.0.0 was over 700MB, my iPad only downloaded a package of about 40MB in order to update to iOS 5.0.1.
The next best thing about OTA updates is that they can be done unattended. They won't be installed automatically, but once you go into Settings > General > Software Update and hit "Download and Install", you don't have to touch the device again.
At the moment, I'm babysitting the device-by-device update to iOS 5.0.0 for the school. This is taking forever. To get to iOS 5.0.1 I can just lay all the devices out on a table, go round them one by one and hit the update button and go home. Next morning, all being well, I'll come in to a set of updated iPads.
Even better than me doing it, though, would be to have the kids do it themselves. This is finally possible because the OTA update process doesn't require the iTunes account password to download. Anyone with access to the device can hit the download and install button. Doubly-better, they can even do it at home (after making a backup in school, of course!).
It makes sense that the update doesn't require the iTunes password, since the iTunes password is not a password governing administrative access to the device. That said, it's a bit surprising that not even the device passcode is required.
The update process will recommend that you connect your device to power but it won't enforce it. It will, however, require at least 50% battery capacity to begin the installation of the OS. Less than that and you'll get an error.
Finally, it's worth noting that you only get the smaller-sized delta updates when installing over-the-air. If you connect a device to iTunes and download the update that way, you'll get the full 700MB+ restore package. It makes sense that this is the case as, if you ever need to restore a device, it's handy to have that package around.
The iOS 5 upgrade from iOS 4 was a painfully slow experience. This is because the upgrade does a full erase and restore of the device. The actual OS update isn't that slow but, because of the erase, it takes a substantial amount of time to re-sync the data, apps and audio and video content to the device.
Obviously, when updating over-the-air, the device doesn't get erased. Total time taken to update OTA was around 10 minutes per device. Similarly, updating a device to 5.0.1 through iTunes is much faster than the 5.0 update because the content isn't erased there either. Total time will be longer in iTunes, though, because the download is about 17x larger than the delta update.
All-in-all, it's a very nice feature to have and a huge time-saver for administrators.