I don't agree with the authors conclusion, but I do agree that tablets aren't usually the right tool to efficiently be productive on. But they're great for consuming. I don't see a problem with that.
I just hope that Microsoft's efforts eventually cause Apple to implement a Wacom digitizer into the iPad.
You're espousing a pretty narrow view of what a computing device can be used for in a way that produces some value for its user.
I'm pretty sure every business prefers a 'narrow view' of what productivity means. The article is in relation to productivity.
I know tons of CEOs who are more productive because of their tablets. The reason is that the form factor makes it easy to carry it everywhere. So they always have documents in Evernote, Dropbox, etc and are able to manipulate those if needed. Sometimes accessing information is the key to productivity.
Now, I am sure someone will want to debate the idea of CEOs being productive, but that is another thread.