"Dropbox is a power user tool/service/feature — a damned good one — just not something the average user is going to leverage in the way that others do. iCloud is a consumer level feature. It’s good enough for power users if they are willing to relinquish control and trust Apple, but mostly it’s a drop-dead simple solution for everyone."
"In that light I truly believe that Dropbox is the past and not the future of cloud based file storage. Managing files is just not something that a user should need to do any longer."
I think Ben is onto something here, but I have reservations about this idea going around that Apple will build iCloud up to the point that nobody needs a service like Dropbox anymore. People have been saying the same thing about other Apple services for years.
Safari's Reading List, Podcasts.app, iOS camera improvements, Apple Maps, iMessage...these are all products that were expected to put entire swaths of 3rd-party services out of business, but it hasn't panned out that way because Apple isn't trying to cater to the same niche markets as those services. They want to reach the broadest possible audience, a tactic that works very well for them, but there will always be a group of people that demands more features and greater control than Apple likes to provide.
I think a key word Ben used in his piece is "trust". Users have to trust that their data is safe with another company, knowing that they have absolutely no way of interfacing with any of it outside of specific apps. iA Writer, an example used by Ben as a fully self-contained solution, could go out of business someday. What happens to that data? Does Apple allow you to export it for use in other apps?
Of course one could say the same about Dropbox, but at least those files exist in a place where you can see them, such as your computer. They're easily copied/pasted elsewhere, and can be backed up in the manner of your choosing. Most users may not care about this, but the aforementioned group of demanding power users will always care about it.
If Apple is really going to put Dropbox out of business, they'll need to allow users more direct control over their files, and that's simply not going to happen. One of the big selling points of iCloud is that it does away with all that muss and fuss.
iCloud and Dropbox are simply two products for two different crowds, and that's okay. There's plenty of room for both to exist.