The upgrade took an hour to download on my iPad today and then about 30+ minutes to install. It is clearly a huge change. I was asked to upgrade iCloud - but will wait until the updates are available for the Mac and iPhone. I do have the ability to share my Apple resources with my husband.
Remember, that when you do any upgrade the Bluetooth is turned on. Turn it off for security and to save battery life.
I am looking forward to using some of the new features. For example, with Messages, I can add a voice mail and share my location. I figured out how to do a voice mail - tap and hold the microphone icon and then slide your finger up to the up arrow to send. I did have not figured out location. More to explore and looking forward to the adventure.