Does anyone tire of hearing about tablets? I am pretty sure I remember some buzz like this around 'tablet laptops'... The ones that the monitor spins around and you use a pen. Turns out those weren't as wonderful as we thought. Almost everyone used the keyboards after about 5 minutes.
Some time goes by, and we get the iPad. Its interesting, but I still don't get the *real* point of it. The device itself isn't particularly useful for business. I've seen them 'forced' into a business and not really work any better than an iPhone for scheduling meetings. The business model was pure creative on top of that, something that Apple clearly caters to with their design cues. Other than being a really fancy calendar and email thing, it was not particularly useful. We didn't pass them around looking at graphs and images, we used the overhead projector hooked to a PC.
Not everyone runs around in fancy suits doing business on the go, smiling like stock photo people... not having time for a PC. Most of us use a desktop. Until something can be *that* useful, its just going to be a 'oooh I gotta have that' thing, not unlike a kid wants a particular toy because their friends have it or they see cool advertising.
I don't think screen size is an important factor, and I also don't think that available applications are the factor. Theres a million for the iphone, yet I only install maybe 10 on mine. Until someone finds a way to do useful database administration, or web development from one of these devices, I don't see them really finding a good use other than entertainment.