Aside from the obvious tactile differences, most mainstream ebooks are saddled with a handicap far more weighty than appearance: DRM or digital rights management.
Those familiar with digital music are likely aware of this issue but it comes down to this:
Downloaded material shackled by DRM licenses are not property of the people who paid to download them. They are considered 'licensed' with restrictions placed on what devices they'll work on, how many devices they can be transferred to etc. Which fundamentally means you don't own the books in your library. I find that completely unacceptable. If I pay for something, I own it. It's mine. First Sale Doctrine should apply to all items--even digital ones.
Intellectual property rights debates have existed for centuries: should lending libraries, used bookstores, etc have the right to lend/sell copies of books? The Supreme Court says yes--copyright owners must get all profits from the FIRST SALE of the book and cannot control what happens further down the stream of commerce.
DRM changes that by treating ebooks as digital items instead of BOOKS. And digital items are governed by the Digital Millenium Copyright Act.
I refuse to give money to an industry that is fundamentally ruining our access to information. Sure, artists and authors should receive compensation for their efforts. But that should not be able to tell us when and where we can use their work after we have legally paid for access.