I don't bother. A few minutes *after* a successful upgrade I will do a hard reboot though. I've found that the first reboot after an upgrade leaves me with blank widgets for a while, so I prefer to get that issue out of the way
I don't reboot before an update but what I do is after an update, I let the phone idle for a few minutes and cool down. I then close all the apps in the app switcher and then shut down and power back on and use the device as normal.