As it stands, iCloud is no Dropbox. Apple's cloud service is about data storage, not file storage - a subtle yet key difference that takes a longer-term view when we go beyond file names but look instead at the metadata stored within.
Dropbox sees this too, and has already released APIs to help apps tie directly into the services and make it more than an online file folder. There are lots of apps that don't support Dropbox this way, and there will be plenty that don't support iCloud's store-and-sync space, either.
But such will be the Apple service's graviational pull - millions of iDevice and Mac users will sign up at the off, this coming autumn - that developers will inevitably shift toward it. Many will support both - plenty will start with iCloud.
Broad developer support will be essential for iCloud to realise its potential and become so much more than an online music locker.
Verdict: Potential Hail
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Mr Punch's Studio