I think publishers should mimic the DVD/BluRay model Disney uses. If you shell out the $$$ for the BluRay, you get a DVD and digital download in the deal. That way you don't have to shell out extra cash for the other formats. If you don't like the film, you can give the DVD to someone else (or the download code) who might enjoy it.
If you buy a hardcover, then you should get a code that allows you to download the ebook version when it's available. That way, even if they put off the ebook availability for 6 months or so, readers don't have to shell out the extra cash for the digital copy. They can give the hardback as a gift and keep the digital or just keep both.
I've yet to see someone stand in line to have an e-book signed by the author.
I note that if you buy a Baen hardcover, inside it you will find a CD-ROM with all the Baen e-books, in multiple file formats.
One of the things we learned in 1992 with ebooks was that at least for early adapters, they tend to be book lovers and geeks.
They wanted the printed book and the ebook, and we worked with Douglas Adams to provide Last Chance to See both as a CD-ROM double set, and as the printed coffee table book.
I would guess that 40 to 50% of my ebooks I've also bought a printed book too, and for some, I have multiple copies of the printed book.
At the same time, I'm really interested in seeing a lot more quality control being built into ebooks. I think ebooks could be a lot better than they are in terms of readability and features.
I love this idea.
I wish more music companies would include a digital download with vinyls, too.