Check the Mac Rumors forums before doing this. I heard that this approach doesn't work anymore because Apple changed some dependencies.

I think you might be correct. Apple used to distribute the Lion Recovery app, which basically copied the InstallESD.dmg to a USB stick, but it no longer works with Mountain Lion. Running this command, however, uses a hidden executable inside the installer application to write itself to a USB stick.

  sudo /Applications/Install\ OS\ X\ Mavericks.app/Contents/Resources/createinstallmedia --volume /Volumes/USBSTICK --applicationpath /Applications/Install\ OS\ X\ Mavericks.app --nointeraction

NOTE: This uses sudo because it needs permission to write to the device. It also has the potential of destroying external drives, internal drives and boot drives. Please change the value for the 'volume' flag to point to the mounted path of the USB stick or SD card you wish to use as the bootable install disk. It will overwrite all the data on that disk. I am not responsible for any data loss using this command. Please double check all paths, all commands and all flags before running this.

What happens when you do that without the --nointeraction flag? Presumably, it explains what it's going to do, and prompts for elevation?

Was the previous comment edited? There's no --nointeraction flag there.

There is, you need to scroll horizontally- there's no text wrapping on <pre> lines.

Copying that file to an external and burning a DL DVD backup of that image were the first steps that I took after finishing the download.

When you install/update the system it creates/update your restore partition. Does Apple still only put necessary file and then do an over the air installation or they put the whole system ready to install ?

I'm not sure yet. For 10.9 the installer put all the necessary files in, and didn't download anything over the air for me.

When installing from one of the upgrade-apps or their bootable USB counterparts it installs the whole thing from the disk, nothing downloaded. The download step is basically just for reinstalling w/o an installer.