That issue is now fixed with OS X Yosemite launching to the public, and Craig Federighi gave a very brief walkthrough of the feature at yesterday's media event, outlining how Mac and iOS apps can automatically generate their own folders for file storage accessible across devices and platforms.
iCloud Drive can also be used in a similar manner to Dropbox, Box, and other cloud storage services in that any type of file can simply be dragged and dropped into the iCloud Drive folder on Mac or iCloud.com and be synced across devices. Access is a bit more limited on iOS where there is no iCloud Drive app allowing access to all files, but the service still allows users of iCloud Drive-enabled apps to view and save files related to that app that are stored and synced with iCloud Drive.
Apple's iWork updates yesterday extend compatibility beyond the core OS X and iOS apps, and APIs are available to allow third-party developers to offer iCloud Drive support for their apps.
iCloud Drive taps into users' general