Taking the iPhone Kindle app out of the picture (though it's probably relevant, I just don't know much about it, so I'll leave it alone for the moment)... Whispernet and software that is in the complete control of Amazon gives them a capability it can't have on my Netbook.
The thing that always concerned me about the Kindle/Whispernet is that they could use it to control all of the content on the Kindle. Lets say Amazon decides that only Kindle purchased e-books are allowed on the device ... one software update later and your imported PDF files are gone (legally or otherwise). I don't think they'd really be that nasty, but it's not as though the software installed is available for inspection. If the publishers push hard enough and the circumstances are right, who knows?
I'm not begging for a GNU/Linux e-book reader. I paid about the price of a Kindle for a low-end Eee PC with a big battery. It lasts about 7 hours (not 9.5 as advertised, but enough). To me, the Kindle is something undefinable. What do I get for $300?. Text to speech on all of my books? Sometimes. The ability to import PDF files? So far. Getting to read the books you purchased... unless...
I "get" that Amazon lives at the whims of their publishers. Unfortunately, the book publishers live at the whims of the consumer and the conditions of the marketplace. They should take notes from what's going on with music today. Scanners are cheap, and OCR software is very good with print. Compressed, text-only renditions of a book are tiny and bandwidth to the home is plentiful. Top that off with an inexpensive device that gets acceptable battery life and offers convenience and an acceptable screen for reading text... It certainly sounds a lot like Napster and mp3's to me.