You probably found that the downloading takes hours, or perhaps you even saw an error message that says the Software Update Failed.
So if this happens with i OS 9, you shouldn't feel like you're alone.
This because the rush will have died down in few days and there might be some initial bugs that weren't noticed in the beta version.
To avoid these problems, we recommend you wait for a day or two to download i OS 9 on your device.
OTA is the easiest and fastest way to update, that's why many people perform the update in Settings Software Update.