Upgrade OS to Mountain Lion

Once it's out and ready to upgrade my OS I'd like to ask a few questions.

So I go to the Apple online store, click to the Mountain Lion upgrade link.
click on whatever is next and it will install it, But what about all my documents I have saved and other things, will they still be there once I've upgraded?

Or do I have to back up everything as it will wipe out what I already have installed?

New Joe said:

Once it's out and ready to upgrade my OS I'd like to ask a few questions.

So I go to the Apple online store, click to the Mountain Lion upgrade link.
click on whatever is next and it will install it, But what about all my documents I have saved and other things, will they still be there once I've upgraded?

Click to expand...

They should be, yes - but anything is possible when you make a major change to your computer, so it is ALWAYS recommended to do a full backup prior to making such a change.

I wouldn't even think twice about Mountain Lion if you don't have an external hard drive with a solid backup.

Or do I have to back up everything as it will wipe out what I already have installed?

Click to expand...

You can do it that way, and indeed, most of us that have been through this a time or two, usually prefer a clean install. But since the advent of new OS X releases being made available from the Mac App Store, it seems that Apple is pretty confident that their upgrade process is pretty bullet proof..