A few years ago I bought a 15" PowerBook with an illuminated keyboard. At the time, I didn't think much of the keyboard:
The keyboard backlight is an interesting idea, and looks very cool, but I’m not sure how practical it is. It’s only really visible when in a pitch-black room, and I can’t remember the last time I used a laptop in a room that dark (save when I was testing the keyboard backlight).
A few days ago, I bought a 15" MacBook Pro with an illuminated keyboard and unlike the first time around I can't say how much I've missed, and how much I appreciate, having a backlit keyboard.
You see, in between the PowerBook and the MacBook Pro I had a MacBook with a regular keyboard. That keyboard was hard enough to read in dim lighting, let alone complete darkness. Now, though, I have no problem reading the keys.
If you're considering between an illuminated and a regular keyboard, might I recommend going with the illuminated keyboard. Even if it doesn't seem like much at first, you'll soon come to appreciate it.