Their DRM scheme is important for those of us who don't have an iPad or better yet have multiple eReaders in the house all of which are NOT iPads. I would be very disheartened to find out that I bought a book from iBooks on my iPad and I couldn't open it up on my Edge. Now they both will use the same ePub book format but since I do not have a way to utilize the Fairplay DRM scheme outside of the iPad, I can't open it.
I also now have to keep a list of which of my eBooks that I buy which can be opened with iBooks on the iPad. If I buy a book which uses Adobe DRm from another store, I have to use a seperate app to read it on the iPad. It becomes a hassle for the reader and has the only objective of forcing a user to buy only from iBooks if they want to really enjoy their eBooks.