If I save files in iCloud, where are they "really"?

If I save files to iCloud in apps in Mountain Lion that support such saving, where on my drive can I find these files if I want to run command line utilities on them, edit them in other programs, etc?

They're located at ~/Library/Mobile Documents.

Each application has its own individual folder under Mobile Documents where its documents and settings are stored.

The folder ~/Library/Mobile Documents seems to be the magic iCloud folder. In fact, if you open said folder in the Finder, the folder name changes to iCloud and it gets a cloud icon rather than a standard folder icon. Pressing ⌘↑ will not return you to the ~/Library folder.