I have an LG VX9800, and it is a minor annoyance, and easily remedied by placing the phone face down, I know...
But I like to clip my phone on my night stand, so that if it rings, I can just look over at it to see the caller ID info without having to fumble for it in the dark.
So, if anyone has found a way to have the backlight off when charging, I would really appreciate a reply!