A lot of what you say here rings true for ipad. It has the same ease of use for purchasing and the same ability to annotate through the kindle apps (though i don't know about emailing doc files to it, I suspect not). I enjoy reading books on my ipad although I think I'd prefer the Kindle for the same reasons - i turn my contrast right down to mimic that of the Kindle. I do use it as a consuming device but increasingly I'm beginning to write and use things such as Documents2Go and Evernote which are very good. I like that I can also read comics on it. It also seems to have the same drawback - namely control by a single corporation. That one company, be it Apple or Amazon, could effectively control the distribution gateway for books (or any other media) is terrifying. Even Google can't be seen to be above reproach no matter what their open source claims might seem to be.

One thing is certain, iPad or Kindle, Android or Windows, these are interesting, exhilarating and dangerous times.