Honestly, on my powerbook, aside from demos to fascinated coworkers, I never used the backlight.
I'm a good enough typist that 95% of the time I don't need to look at the keyboard. In those cases that I needed to, the backlight from the display was enough to see the keys.
I did found it very annoying in mid-light conditions though, there would be a point where the light would turn on, but it just blended in with the keys, and made it look like the keys were unlabelled -- I didn't need the labels, but from an aesthetic point of view it was annoying. Then it would get darker, and the backlight would start to become distracting.
I really don't miss it with the MacBook.