I've done a couple and they seem to go pretty smooth.
Couple things:
- Pull a drive before you start. (quick restore if something goes wrong)
- If you have failover installed, I would uninstall failover and then reinstall after the upgrade is complete. I have had issues with this during the upgrade
- Upgrade your TSPs 8.3
- Follow the steps, dont skip anything
- upgrade will take a bit of time depending on the size the current SQL database. Expect around 2 hours. SQL database is upgraded during the process
Good luck!