The content acquisition problem is just as important, or even more so, then the hardware problems for any electronic media device. Someone using a competing e-reader has to navigate a number of competing e-book stores, download and keep track of their copies on their own storage media, and then sync books over to their device via USB or storage device; that's a lot of work when you just want to read a book.
I remember reading about someone who described how he'd walk into airport book stores, lazily browse through their books, and then remotely download his favorites onto his kindle; that's powerful.
Instant gratification works both ways. If I really need a book on something, I will go the local book superstore, browse through them and read the reviews on Amazon.com while there and buy (price insensitive) the one that seems the best. Pre-iPhone, I would read the reviews on Amazon.com and then call around to hold it.