Many points of the article are related to conflict resolution and CoreData sync, both of which features that are a) incredibly hard to get right and b) practically unsupported by Dropbox. Dropbox' method of conflict "resolution" is to keep to files around and its method of synching databases is to not do it.

There are other places where Dropbox has advantages over iCloud (like doucments being shared between applications, even though the dropbox api seem to move away from that and on to sandboxed application folders), but for the points made in the original article, Dropbox provides no help at all.

No, the article covers this. Dropbox is great, but it is based on document syncing. Apple has document syncing working just fine. Like database synching, Apple and Dropbox both have issues. To get a hint of the problem, you can read this post about why git+Dropbox is problematic: http://www.unityisplural.com/2012/02/git-dropbox-bad.html (I've used git+Dropbox and have gotten corruption issues in my git repo).

Further, by pushing an app relying on Dropbox, you're telling your users to sign up for an extra service to use your app. That's bad.

It's true that git+Dropbox isn't resilient in the face of multiple simultaneous writes, but I think the problem is overstated. You might see an inconsistent state, but you'll never get corrupted data because of it. You might corrupt the repository on Dropbox (has happened to me a couple of times), but this is trivially fixed by deleting and recreating it.

I'd never use it for a large team, but for a couple of collaborators, or syncing a repository between multiple computers for a single developer, it's a nice and easy solution.