Why am I willing to make these trade-offs for CloudKit, despite it’s limitations? Because, ultimately, developer perspectives aside, I felt it was the right choice for my customers.
They will not need to setup another account with yet another set of credentials to manage. More importantly, their data will be stored with Apple, a vendor they have already choosen to trust. It will be stored in siloed, private data stores that not even the developer can access. That cannot be said for apps using Azure, Parse or other backend services.
This is one of the biggest reasons I want CloudKit to succeed. As a user, it's easy to get started with a CloudKit-based app because you (presumably) already have an iCloud account. That means more time exploring the interesting and unique things the app can do, rather than messing with accounts and credentials. And the privacy aspect is significant. I'd argue that Apple takes user privacy more seriously than any of its competitors. (Whether you agree with that or not, Greg is certainly right that users have chosen to trust Apple with at least some of their data by virtue of creating an iCloud account.)
However, these advantages may also limit some of CloudKit's possibilities. As I describedin my earlier post, the inability to move data off of CloudKit is one of my key concerns. While it's conceivable that Apple could add data export to CloudKit in the future, it's hard to imagine how they'd do so without compromising privacy. It's possible export could be limited to public data, but that might limit the utility of the feature in the first place. (For example, suppose Vesper used CloudKit at launch, but then decided to move to another service. It wouldn't do them much good if they couldn't migrate everyone's notes, which would presumably be stored as private data.)
As Greg pointed out, CloudKit holds a lot of potential benefit for users as well as developers. On the other hand, users won't see much of that benefit if few developers adopt it. Hopefully Apple has (or will) strike the right balance so that we all reap the rewards.