Of course, "taking" 90% of a market is a different achievement from "expanding" a market to 1000% of its prior size, which is more what Apple did here.
That is, if the prior-to-iPad market was 100 units, and the iPad sold 900 units, then Apple has 90% of the resulting market -- yet they haven't taken a single unit away from the prior number.
I'm only quibbling about the word "take". What Apple did was expand the market by about a factor of 10.
IMO, sales market percentages are among some of the most awful, misleading, and pointless statistics in existence. They have to be treated with suspicion. :)
Since the numbers come from the sales and marketing folks, I thought suspicion was a given.