The consensus as of today is 10.1" diagonally. In other words, I would get a nice leather sleeve and keep it in my Timbuk2 bag.
OK, so if only a 10.1" version is available, and how we carry it about is in a Timbuk2 bag, then we go right back to why this vs. a (seemingly more powerful) laptop that we can carry around with just about the same full mobility, in that same bag, and through which we should be able to consume that same (new iTunes) content, and so on.
I'm getting jumped here (my favorite was "haterade") because I'm actually genuinely interested in the thing (I haven't yet purchased an iPhone or Touch because I find them too small for my size). I am a huge Apple fan, and I own a lot of Apple hardware. My iPod is nearing retirement as is my Powerbook G4. So here's a device that could probably fully replace that iPod... and maybe (but I imagine less likely) replace that notebook in my equivalent of a Timbuk2 bag, as a smaller, thinner, lighter package. I think that makes me a bona-fide, great prospect for this Tablet.
So I'm asking questions trying to get at an answer for the thread's original question. From one group, I'm getting answers (mostly) to other questions such as all the benefits of print media going digital, and how much easier/better it is (somehow) going to be to consume this content on a (smaller) screen instead of a screen with a hinge and a keyboard attached. While several of those kinds of points make great sense, very few of them depend on the availability of a Tablet product to be realized. The best of that bunch gets down to modest benefits such as maximum portability, always-on convenience, cool, thinner & lighter, etc. (great stuff no doubt, but is it great enough to move the mass market to spend (my guess) $799 or maybe the $1000 rumored from a more connected source.
On the flipside, there is this other group who sees no purpose for this thing at all... often because whatever
they have for
their own needs should be perfect for everyone else too. For example, this thing shouldn't have 3G functionality as an alternative to the iPhone because the iPhone should be the only phone... or they have an iPhone and don't want to pay for iPhone hardware in another device (so no one else should be interested in that functionality either). But I don't have an iPhone and if this thing could cover that base for my needs then it would be much more appealing to me ( a very tangible benefit to help support whatever the price might be). And interestingly enough, some of these same people think a price for this Tablet just a bit above an unsubsidized iPhone is nuts, so they want the rich wonders of this device at a significant discount vs. the smaller-screened iPhone, such that they are dismissing the most obvious way to get the low pricing (and still pay Apple what they really want in TOTAL for this device)... the option for someone else (AT&T, Verizon, Tmobile, etc) to chip in a good chunk of Apple's total price.
If 10.1" is it, it collides with the choice of "take the laptop or take the tablet?". It seems much less likely that someone will throw BOTH into the bag, if they don't want to carry 2 bigger screens when either one can do most of the jobs. In my imagination- even if it is really a "wow"ing device- unless I can do the work I do on it just about as efficiently as what I do on the laptop, I take the laptop and leave the Tablet at home (or don't buy the Tablet at all). If I have to also pack a- say- bluetooth keyboard with the Tablet to approximate that popular mode of getting work done (producing content), then it's not as "thin and light, etc" when all the pieces have to be included in the bag (why not take the probably more compact laptop?).
Do I think 10.1" would be great for content
consumers? Absolutely. Bigger is definitely better for consuming a movie, TV show, reading print media gone digital, etc. I just find it harder to imagine the broad market appeal of buying a Tablet if the vast majority of benefits can be realized on other iTunes-connected equipment we might already have... certainly not like the obvious market demand ahead of an iPod and iPhone. Maybe all this wonderful new content will be
exclusively available to the Tablet owners, which then would be another tangible reason to need/want a Tablet and potentially justify why you might want to throw both it and a Laptop in the bag. But that would then come with its own headaches for Apple, and all these new content producers would seem to want to be able to sell all this new content to the millions of iTunes users already in place, not just the Tablet buyers to come.
To each his own- as it should be. I'm still hunting for a great answer to the thread's original question, qualified by a best guess at price for whatever the Tablet imagined will cost. The best I've seen that does both in more than a 1000 posts is Rocketman's post several pages back. It basically makes the Tablet very appealing by using the razor blade model: give the shaver (Tablet) away and make all the money on the blades (content/connection). I do believe THAT would "sell" a LOT of Tablets even with the issues I've pointed out above.