i have a kandle (
http://www.amazon.com/Kandle-Designe.../dp/B0031116K8).
It lights up the top of the kindle really well and diminishes towards the bottom (like every light). It bothered me a little but eventually I got used to it and it's not that big of a deal anymore.
For me, it's not so good when you're borderline (between needing artificial light or natural sunlight).
But when it's very dark, the kandle is very good. Also, The Kandle is very portable. It just folds up and you can leave it in your pocket or something.