My understanding is that Amazon's rolling over means that they won't be limiting their selection. (Granted, the Macmillan titles aren't back yet, but all the announcements from both sides indicate they will be.)

On the other hand, it doesn't sound as if any vendor will be able to compete on price (since the publishers will be setting that themselves). So I don't know on what basis they'll compete. Maybe convenience, multiplatform options, and who can get their devices with their store as the default into the market fast enough.

I wonder if the agency model forbids offering rebates, points to be used for future discounts, coupon codes, or other marketing gimmicks, or if it just specifies list price and how much the publisher expects to receive from each transaction.