How to update Xcode?
Solution 1:
Just an extension to this. I'm using OSX Lion and you can install/update via the App Store.
Solution 2:
To update Xcode, sadly, you have to download the entire .dmg file from Apple's website again.
Solution 3:
I recommend installing into a different folder in the root of your hard drive. I have had problems in the past, not with this specific upgrade, that were fixed by doing a fresh install.