I think a lot of this will shake out in the future. First adopters always pay a higher price. BUT...
One of the main problems of comics in general is that the product is too pricey for the audience that they were originally intended for (pre-teens and teens). Digital will be their opportunity to start picking up that market again. But not at those prices.
Here's a pricing structure that would entice me to run out and buy an iPad today:
*Early comics (released on Monday rather than on Wednesday) would cost cover price - I would reserve this for the ones I was really dying for.
*New comics (released on Wednesday) would cost cover minus 15%(same as LCBS's) - I would probably buy 3-5 comics a week, mostly outliers
*3 month old comics cost cover minus 25%
*6 month old comics cost cover minus 50%
*1 year old comics cost cover minus 75% - I would, most likely duplicate all of my top of the pile comics with these. AND, spend a fair amount of $$ on old, beloved runs.
*A sub to a comic gives you the digital free. Same with a TPB.
*Any Digital comic purchased/owned gives you access to a later Directors Cut, and Varient Covers.
And those prices would extend back all the way, so a comic that cost you 10 cents, the digital would cost you 3. Think about it. No-one is going to buy Amazing #12, 54, and 123. They're going to buy the run (or mini runs). By my calculation, it would cost around$200 to buy all of Amazing my way as opposed to the approx. over $800 that they're proposing. Still pretty steep, but doable.
Don't get me wrong, I don't expect anything like that in the near future. But I think that'll have to have something more along those lines for people to respond in any great numbers. AND, until they have a large catalog (of digital) comics, a lot of it's a moot point anyway.