One major question that I have for everyone who upgrades iOS on launch day is, "why?" Nobody upgrades non-Apple operating systems on Day 1. Sometimes people wait for an entire year to upgrade the OS, because the device is functional at the old OS and risks becoming nonfunctional with the new OS.
Yet I continue to see people upgrade OS X and iOS on launch day, often with predictably regrettable results.
I make my kids upgrade their iPads first then test them thoroughly before I do my wife's iPad and iPhone.
With respect to OSX I go for a major release straight away and test it for a couple of hours. If it's broken, I'll restore the machine from Time Machine.
All the Apple users I know do roughly the same process. They're quite conservative and pick guinea pigs before they upgrade.
I've always upgraded everything as soon as possible. This is code that has been written to improve existing code. Bugs have been fixed, security issues patched. Testing has been done, and it's good enough to push to customers.
I've always done this, and short of when I used Debian Sid (I think it was), I've never been bitten by it.
Yet I continue to see people upgrade OS X and iOS on launch day, often with predictably regrettable results.