It sounds like you are one of us who already reads for hours at a time with a backlight, and have not experienced the fatigue issues some of the others have had. If you want one of the eInk displays though, you are stuck for an integrated light -- unless you want to go the do-it-yourself route, in which case you should check out the accessories board in the Sony Reader section. Lots of neat Frankenstein-esque ideas there.
I am lucky in that I use a backlight and have no trouble even with long sessions... Just read my way through a four hour flight yesterday and read some more when I got to my hotel room. The battery life is an issue, but if I keep the backlight relatively low, it seems to solve both issues. My eBookwise is very usable with the backlight set at about 30%, and it runs for 19+ hours. Of course, it just does not look as nice as the eInk displays do in good lighting. The versatility was a good trade off for my sitch, though.