When I first began testing different ebook formats a few years ago, not only was the iPad hardware superior to the Kindles and Nook, the ePub reading experience in iBooks was vastly better than the same ePub on the Nook or the .mobi equivalent in the Kindles.
Where Apple failed was in the purchasing experience (the iBookstore/iTunes mess) and some of the back-end tools for publishing. Other than updating the iTunes Producer interface for submitting new titles, and improving iBooks Author for Apple-only rich media ebooks, I haven't seen any significant improvements for readers or publishers who want to use the Apple platform over the past two years. Meanwhile, the Kindle Fire has brought Amazon customers a slick alternative to the iPad at a much lower price point.
I don't like having an Amazon monopoly, but some of the blame should be assigned to the erstwhile competitors who can't seem to get it together.