It seems something else than gnome-power-manager manages the backlight dim timeout on Thinkpads, maybe thinkpad-acpi. How do you alter the timeout from 5 seconds? (which is very annoying)
I'm using an IBM Thinkpad X21 as a 3G router. It's running a server install of lucid. The laptop has the lid up most of the time. There is no X, just a plain console. The colsole blanks itself, but ...