I really wish they had gone with a transflective screen, like Pixel Qi's..
It's not for me, but I can definitely see the allure for a certain (large) segment of computer users.
Once something like this comes out with a transflective screen, I might pick one up. Typical LED/LCD screens are too difficult to use under bright lights.
A back lit screen might not be great for reading on a sunny day, but for someone like myself, who has had to give up reading actual paper books because I can no longer see them, and is stuck reading only eBooks where I can have a back light and enlarged font, the iPad is exciting. Finally, I'll be able to relax on the couch again and read comfortably, rather than having to sit at my desk.
I do realize I'm in the minority when compared to the overall consumer market, but there are a lot of visually impaired users who would actually benefit from the back light.