I've now had nearly every version of the Kindle (original, Fire, and now Paperwhite).
I read about 40-50 books a year, and travel a lot, so the Kindle is a Godsend.
If you only read books the Paperwhite is for you.
- I tried the Fire but you can't read in direct sunlight, so it's no good at the beach or outdoors.
- I never used the Fire web browser, typing is just too tedious (swype on the phone is easier)
- I tried reading newspapers and magazines on the Fire, which was an exercise in frustration
- if you leave the Wi-Fi off on the Paperwhite, the battery lasts for about 6-8 weeks of daily use
- the Paperwhite reader is easy on my old eyes
If you have a Kindle, get Calibre. With that program you can convert any book format to Kindle format.
With Calibre, you can also enable "Heuristic Processing" which fixes most of the formatting issues.
I'll occasionally read a hard book, but it becomes tedious after only a short while with the Kindle (I was the guy who said "no way, never" to E-readers, till a buddy gave me his old Kindle)