This article was explaining why Kindle (the software, not the device) has won. Kindle is available for the iPad (and the iPhone, where iBooks isn't yet available) and anyone who already has a large library of Kindle books will be more likely to stick with Kindle than move to iBooks.

The device is going to struggle (I think Seth Godin's suggestion to reduce the price to cost is a good one) but the software is where they need to win in order to accomplish what Amazon really wants: a large market share in eBooks.