This month marks a year and a half of continuous use of the Kindle Keyboard (used to be called Kindle 3). Between those months of use, I've had the opportunity to own other tablets and use other reading formats but I keep on going back to the simplicity of the Kindle.
It's probably because of E Ink which just works. I've always been a fan of the display technology when it was introduced. Now its being used in other products such as wristwatches, retail displays, etc. I hope Amazon continues to build E Ink based Kindles and perhaps even move to Color ePaper technology.
Regarding formats, the only thing I'm not really happy about is not being able to support ePub, while the rest of the competition has adopted it. Even the new version of iBooks for the iPad supports the latest version of the ePub format although there are reports that the support is broken in a way that Apple added undocumented extensions that pretty much breaks the standard. But I don't see myself using a lot of iBooks in the future even though the books are pretty. The problem is that the file sizes are too huge (the Life on Earth book is almost 1GB).
It's amazing how ebook technology has evolved over the years. I remember in my previous work, the first time I had a chance to work on ebooks was when we had to do some work on the Franklin eBookMan. It was a terrible device to begin with. It didn't ship with an OS, you had to download it first before actually using the device. At least it had support for Mobipocket format (before Amazon bought them). When I started reading books and building content for the eBookMan, I got hooked and have always been looking forward to ebook reader technologies that come out since then.
Hopefully, Amazon continues to develop the technology for dedicated book readers without resorting to LCD or LEDs. The E Ink Kindles work just fine and have a market of their own. Heck I wouldn't be surprised in a few years, Amazon will just give them away to any Amazon Prime subscriber.