- Availability. Within the US (and only within the US/Canada) book availability is great, but it isn't perfect..outside the US/Canada it sucks. Amazon once had books 1,2 and 5 of a series I wanted, but not 3 and 4 (I know, i know, this isn't amazon's fault)
- Price. Kindle books are often more expensive than their physical counterparts
- Quality. Not only are you paying more, but you'll get OCR errors in every book.
- DRM.
The above 4 combined make it so I rather donate to Calibre (http://calibre-ebook.com/) and find other ways to get ebooks onto my device.
Additionally:
- KDK. The KDK isn't public yet, and it seems imposible to get into the beta. On top of that, the KDK is lacking some basic APIs (like collection management)
- Indie support. It's my understanding that you can't publish a free book as an independent author to the kindle store.
My plan is that when it's time to upgrade (hoping for a new batch of options for xmas), I'll buy whatever has the best screen/battery/dimensions/weight/price. Because, really, once you don't care about the Kindle store, there's no reason to not simply get the best device. Amazon doesn't do any value-added with the Kindle....there's no reason to be loyal or stick with it.