Not to repeat what others are saying, but I have a Kindle Fire and my wife has an iPad. I think the reader on the iPad is a little better than the Fire...
However, I travel and like that if I lose my Kindle, I'm not going to be out as much as an iPad. So that is a factor to me.

I have apps on the Fire for when I don't want to just read.
Battery life is fine and I've never had an issue. Does it last as long as the non-Fire Kindles...probably not, but it's never run out on me on a flight.
I also like the free "Loaner's Library" for Kindle owners.