Not mentioned so far is that AAPL owns the supply chain. Competitors need to have access to the same parts in the same quanities, but they cannot buy what is already sold to AAPL.
Catalogue makers want high-res displays for their products - only the new iPad offers resoultions equalling high end print, medical professionals have already snapped up quanities of iPad 2s but the new iPad will make their 10K desktop an antique. Would you rather a doctor looks at your x-rays on an android, ansus or on some crappy 4bit tablet display?
A million more pixels than an HD TV is saying something.
Then there is the USAF buying 18,000 of them.
One must keep in mind all those vaunted competitors are up against the largest compay in history.
And that compay makes its own hardware while the competitors buy off-the-shelf componets - meaning it just a question of who connects which part to another in which order - they are all the same thing, with only the OS and other software to distinguish them freom each other.
I think the competitors were so busy making cheap stuff that when the iPad showed up, they were fast asleep and only now are trying to rose themselves only to find they have been Left Behind :)