Via iTunes. Usually I do a clean install with no backups/set up as new, but this time I was admittedly lazy. It worked out though so I'll save clean slate installs for problems that warrant it instead of wasting my time in the future.
I used iTunes because I updated a week before the public release when OTA was not an option yet. I really had no choice but its the method I use the most anyhow. My kids keep their devices full. OTA will struggle or not work at all with full devices but iTunes has no issue with this since it downloads and processes the update on my PC versus the device.