As much as iCloud is the right idea still not realized, Dropbox is the wrong thing done brilliantly well. And at the end of the day, that still amounts to the wrong thing.
Those of us used to, and clinging to, traditional file systems love it, and will continue to love it as it becomes marginalized into obsolescence, as the growing mainstream -- those who aren't power users but are increasingly empowered users, and who won't get it and shouldn't be subjected to it -- sweep past it and into newer, better things.
iCloud could be that better thing, if Apple can nail it. Big if. So could something else, including a new version of Dropbox. But nothing and no one is there yet. So, as iPhones and iPads and other appliances bring computing to a broader user base than ever before, the services that bind them remain stuck between the best-ever version of the past, and a still sputtering and stammering future... More at iMore.
Decent article by Rene. I personally rate Dropbox very highly and iCloud about as low as is possible, but agree that changes to both could make one the killer Cloud service. However, I have seen no indication yet that Apple is capable of improving in this area.