He fails to define what criteria he uses to call them underachievers. In fact, the current crop of so-called Tablets are nothing more than the same kind used in check-out counters or information kiosk and should be termed as touch sensitive device.
It cannot write like Windows Tablet that stores the scribbles as searchable ink. It cannot write and convert to text as you write. It relies on a touch senstive keyboard, which has been found even in good old PDA, and in an integral part of Tablet Windows. In fact Tablet Windows has 2 touch sensitive keyboards - one fixed one and another floating one. The current crop of non-Windows touch sensitive devices cannot provide the user with the ability to annotate, scribble and mark up any documents.
Windows applications run without modification on tablets; my Firefox can use the tablet input and my Thunderbird, with GeckoTIP, works flawlessly. It offers developers ability to develop ink-aware applications that you can scribble on say a PDF or Word documents just like you can do to a printed document.
Sure the current crop of touch sensitive device has gesture to open, zoom, flick or rotate object. Windows 7 touch sensitive netbook and Tablets have that functionality in addition to use stylus to write. That kind of gimmicky stuff is nothing new but is a good bait for technical bloggers or reporters.
The only thing working against the current crop of Windows Tablet is the price. For a properly functioning tablet supporting stylus, it is a lot more expensive than touch sensitive only device. Until the screen cost can be reduced further, this handicap will continue to exist. No amount of software can overcome that.
As a long term Windows Tablet user, and is still using one to compose this blog, I have found the current crop of touch sensitive devices, like iPad, Dell Streak, even Windows touch sensitive netbook, lacking. The ability to write/scribble notes or to annotate pre-prepared document in a meeting or presentation provides a dimension these touch sensitive devices cannot meet.
The convertible type, degraded by Dan through his obvious lack of usage over a period of time - the one with a hardware keyboard - are the most versatile of the lots. While one can write, with some practice, comfortably a reasonably long document using the stylus, often time the keyboard can give you that much more speed and precision. Of course the current crop of touch sensitive devices like iPad are not composing devices for "business-oriented" operations and are more a presentation device, more like a large size iPod Touch. As a result, there is no need for a keyboard with feedback. In a convertible or hybrid kind the keyboard complement the stylus.
So who is lacking and underachieving - show me how to annotate a PDF on iPad or running something like Excel, Photoshop or other productivity suite on iPad like devices.