I personally don't have the kindle fire. (I have the iphone so I downloaded the kindle app and just use that). My friends (husband and wife) both have their own and they love it. Im talking about they are always reading a book for messing around with apps on there. Im not really sure how the apps work- but I know she can get on facebook from her fire.
I have also heard good things about the Barnes & Noble Nook. Not sure if you have looked at them at all. I did when they first came out. They have a feature where you can be inside the book store (drinking coffee or just enjoying the quiet) and you can read books for free. You have a certain amount of time, but if you work or live close to a B&N you can go in for your lunch break or something like that and read a full book thru out the week. Another feature they have is if your friend also has the Nook, you can share books for free. I believe its 2 weeks at a time, then they charge you for it. But if you friend buys it you can read it for 2 weeks, then give it back, then get it again so you can finish the book.
I have a friends mom who has the original Kindle and she is always reading it. And my grandmother got a Nook for Christmas. The only reason I never bought one is because I love holding a book and reading it. If I am spending the money on a book, I want the physical book in my hands. And another reason is my husband and I read the same books, so when Im done he reads and vice versa, so it would get to be a pain always waiting to get my hands on the kindle.
I will say tho that I have heard great things about the fire.
My sister has the kindle fire. I have the kindle touch (I'm into simplicity). She loves it! Hasn't had a single complaint yet. Apparently it's so simple, even my 2 year old nephew has the Thomas the Train stories figured out as far as how to turn the pages and where to touch