OK, getting back to the Kindle thing...
I like :
Making the text big enough to read without glasses
Buying a new book while on holiday
It's far easier to pack than a whole heap of books
A 3G one (like mine) will get you onto the interwebs anywhere there's a mobile signal.
I dislike :
No backlight (although the new ones have one)
Needs charging occasionally
Can't swap books with friends
The web browser is a bit rudimentary.
Kindle on a smartphone is great, provided you've got a data connection. And you don't mind charging the phone every day, but you have to do that with smartphones anyhow...