I think we'll only get large numbers only when a device

arrives that is the best option (or at least functionally 

equivalent to the best option) available for its primary

purpose.

iTunes gets big numbers because it's considered the

best option for acquiring, storing, and listening

to music (with a babelfish-type device in your ear).

iPhone gets big numbers because it's considered the

best option for making and receiving cell-phone calls,

plus (see iTunes).

There's nothing on the electronic horizon (except Kindle)

as a candidate for easily acquiring, storing, and reading

books in a format equivalent to the printed version (which

is why PDF is critical.). Not ebooks, books. Whether it's

there or not is debatable (although Oprah seems to think

it is, and she sells a few books now and then.) But if it is,

or at least to those for whom it is, price is a secondary

factor.

I think the "acquire" issue is more important than is

generally conceded. This is why Microsoft will come

in a poor second for any device it puts its name on.