I find this wildly at odds with the experience of my friends. Granted they are early adopter type folk but they have taken to tablets extremely intently. They use them for gaming, and browsing, and other miscellaneous activities. Just because they are not great at everything doesn't mean they can't be incredibly useful tools.
The author talked about "productive use" - you listed gaming and browsing. In many circles those don't rank as productivity. There's a fine difference between "great"/"cool" and "being productive".
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.