Generally upgrades and updates go smoothly, but not always.
Although Apple have made firmware upgrades a painless process I still hold my breath every time. Bricked to many devices in the past…
He’s not the only one who holds their breath…
I do it quite often, especially with firmware upgrades.
Having said that, I actually now rarely upgrade unless I am “forced” to. Sometimes I have been “forced” into an OS X upgrade as a piece of software I want to use is only compatible with a newer version.
If it works I generally leave it well alone. In the main as updates sometimes just do weird things.
Good example, I upgraded the iPod touch to 1.1.3, but I ain’t upgrading to 1.1.4 just yet.