Some additional images and video of Courier, Microsoft's tablet PC that may-or-may-not be the purest vaporware, leaked late last week--Engadget started it off with some nifty photos of what's purported to be the user interface, along with a prediction from an unnamed source that the tablet will launch in either the third or fourth quarter of this year. Other online reports have suggested, through their sources, that a possible release date will be 2011 or even later.

If Courier is indeed on a development track, I suppose that Microsoft executives are waiting to see how the tablet PC market fares overall--not only in terms of Apple's iPad, which is due to hit stores on April 3, but also products such as HP's tablet that CEO Steve Ballmer showed off at January's Consumer Electronics Show. (Microsoft continues to not comment on rumor or speculation, even after I offered to take it to a really, nice swanky place for dinner and not order the cheapest bottle of wine off the list.)

Courier would look like nothing else on the market: two touch-screens that fold on a central hinge, like a paper notebook, and are capable of all sorts of nifty things: displaying e-texts, sketching and writing longhand, Web surfing, and viewing that Iron Man 2 trailer that debuted yesterday and is basically the most awesome thing, ever, period. The device shown in Engadget's leaked photos measures 5x7, and at least feels a little smaller than the images that leaked on Gizmodo all the way back in September.

It also feels a little something like a niche product--the sort of thing you'd see produced by a boutique manufacturer, in limited quantity, for a higher price-point than similar products on the market. Except that's not how Microsoft plays the game--as has been reinforced by executive from Ballmer on down over the past few years (particularly in the context of conversations about the company's competition with Apple), Microsoft likes to spread itself as widely as possible.

"You can't be high priced," Ballmer told a group of analysts at Microsoft's annual Financial Analyst Meeting back in June 2009. "That doesn't get us to the high volume that we aspire to."

So if Courier finds its way out of the lab, chances are Microsoft will want to make a substantial push behind it. But the success or failure of such an initiative depends on how much the public has gravitated towards the tablet PC form-factor, and how willing they might collectively be to try something other than the traditional tablet form.

Although I can't back it up with hard numbers, my intuition tells me that tablets will be a middling success, at least in the near term. Millions of marketing dollars will go to ensure a certain rate of adoption among the particularly tech-savvy and the usual first adopters, but penetration among the general public is a grayer proposition; particularly when you consider that discretionary spending on big ticket items is still fairly suppressed thanks to the aftermath of the global recession. If your typical family already owns a laptop, and a television, and a smartphone (or two), and maybe a desktop PC, then are they really in the market to own another computing device?

The answer to that may determine whether the iPad and its competitors will be the truly paradigm-shifting proposition that some analysts suspect. If the whole concept of tablets crashes and burns, though, expect Courier to stay firmly in realm of vaporware for the foreseeable future.