This is pretty tempting, I am on my PRS-650 and having issues lately with battery life. I COULD just replace my battery I suppose, but I have been interested in the built in lights since they released a couple of years ago. I can't believe Sony has dropped the ball on implementing it in their new readers so far.
I have to say I've been happy with the PRS650 software and the build quality of the 650, though the newer Sony's don't seem as nice. I bought my wife a Kobo touch reader a couple of years ago and it seems fine, I don't like it as much as my Sony due to the lack of some features, but it was 1/3 the price too..
I am hoping Sony will pull it together this year with a light and maybe a better build quality. I may jump on this one instead though. I wish I could see the Kobo's locally though, I went to B&N and looked at their lighted reader and you can see a gap between the bezel and the edge of the eInk screen, which becomes VERY apparent when the light is on. I guess I'm just spoiled by the 650.