Chris Rawson, writing for TUAW:
Mac OS X Hints has discovered that Macs running OS X Lion and registered with iCloud have a hidden "drop box" in the user's Library folder that allows for easy document and file syncing between Macs. A folder within ~/Library (which Lion hides by default) called "Mobile Documents" contains iWork documents synced with iOS devices via iCloud. I saw this article a few weeks back and have been to busy to post it. This gives me a lot of optimism that perhaps, one day, iCloud can replace Dropbox for me. Hopefully within the next year, even.