There are USB LED lights on a flexible cable that holds its position that might be a useful add on for you to light up you keyboard.Yes it is a deal breaker. I actually spend quite a bit of time in bed after lights out surfing and reading, keeping up with stuff (I am doing it at this moment) with the brightness at the lowest level +1 to not disturb my wife, and its definitely not enough to see the keyboard.
I also like it for taking notes in a dark presentation room. I got the newer air and returned it after a week (and gladly paid the restocking fee) because of this alone. I really liked the reduced weight and bulk, didnt miss the optical drive, but I gotta have that keyboard backlit.
right now I tend to use the ipad when I am just reading, but when I have to type it gets awkward, so I break out a laptop.
I understand what and why you want back lit. What I believe is Apple is striving for longer and longer battery life ... and many of us are touch typists and don't even look at the keys at all. If you consider the iPad ... one of its key features is outstanding battery charge. The AIR is the next step up and offers interfacing the iPad doesn't. The next step will be thunderbolt for high speed data transfer to the higher performance Macbook Pros, and iMacs.
I know the add on USB light isn't built in but is a viable option for the few that need the backlight. Either way that option draws more power. sobeit