Convenience to whom?
Interesting article but I think you missed the real driver behind the public IaaS adoption, developers!
Anyone who is using AWS in a big way is most usually a developer who went there because their own internal IT platforms were slow and a bit rubbish. Developers couldn't give a crap about the platform they run on, all they want are programmatic API's, instant response, and the ability to get on with their job. So your absolutely right, its all about convenience for the developer.
Couple that to the fact that most private clouds aren't even clouds, VMware on a bit of tin (even if its "converged") is not a cloud, show me a programmatic API, then I'm listening. The complete shambles of traditional vendors and SI's pushing "private" cloud that's been happening over the past 3 years has helped drive people out.
Now for the "but", there are numerous organisations who whilst starting in public have come across the big problem. Cost! When your application hits mainstream and you have a nice base-load your suddenly hit with the realisation you are paying an awful lot, especially when finance start crunching some numbers.
That's when people start to look at building internal clouds, difference is they now have to build platforms that look and feel to their developers like a public platform (i.e, API driven) and that's when the lack of open becomes a big problem. Ever tried to move an AWS app on-premise?
So now the conversation about open platforms becomes important. Its also true that customers are smart about not being locked in, first "open" Unix killed the mainframe, then x86 killed Unix. Developers themselves are mostly using open source tools and technologies so it makes sense to have the platform open as well!
By the way the whole "OpenStack is hard" argument is a bit old and quite frankly smacks of a lack of research, there are plenty of decent supportable, install-able distributions out there now that means a customer doesn't get their hands dirty and have to worry about how it works.