I'll break away from my perma-lurk and share my Kindle experiences. I got my Kindle in March and have read about 15 books on it so far. In that time, I think I have used the keyboard twice. For the most part I only use the Back, Home and page turn buttons. I find it isn't really a necessity.
You can join pretty much any network, so as long as your phone is acting as a hotspot, you should be able to connect to it. I have the WiFi only version and I've not had any problems. Typically I have it loaded up with books so I don't actually have to be online for anything. I have purchased one book via the Kindle itself without any problems. Unless you run out of books away from some WiFi, I'm not sure why someone would want the 3G. I mean, it has some "experimental" applications like a web browser and music player but I've not messed around with them.
I've had
this Timbuk2 Kindle case since I purchased my Kindle, and I've never had a complaint. It has a nice soft interior that protects the screen and also absorbs a bit of shock, if you drop it.
I looked at the Fire when it was announced, but I find it to be a lackluster tablet. One of the things I do like about the Kindle is that it isn't back lit so it is very easy on the eyes. That said, I have found myself in darker areas (certain parts of Metro, etc) where it is hard to see the screen without some lighting.
Overall, I love my Kindle. I don't miss the "book" experience some people have when moving to an electronic reading device. Although, my largest complaint is that I can't read during take off and landings while flying (no fault of the Kindle, mind you).
edit: I forgot battery life. Since March, I have charged my Kindle twice. I keep the WiFi off, and read it almost every day on Metro - occasionally before bed as well. I'm greatly impressed with the battery life on this thing.
Edited, Sep 29th 2011 12:07pm by Dozer