I clicked on the install button on the Mac App Store to install Xcode for Lion. But then after the download was done, nothing happened. If you are in the same boat, keep reading.
It turns out that there is this new thing called Launchpad on your dock. The “Install Xcode” icon is sitting there for you to click on. But before that, do the following to save you trouble.
First quit your itunes. Simply Cmd-Q it.
Then open up your Activity Monitor, Force Quit the itunes helper.
Then either go back to Launchpad to run “Install Xcode”, or at Spotlight, search for “Install Xcode” and run that. You will then proceed to the Xcode installation process.
I got stuck at “updating files” towards the end. If that happens to you, force quit the “Install Xcode” process, then quit your Mail and iCal programs, then run “Install Xcode” again. I don’t know why or how or anything, but this worked for me.