With regards to #3, this can be partially fixed by disabling a gconf key. In particular, /apps/gnome-power-manager/backlight/enable ... Disble this and AC unplug is fixed, but brightness key still has same affect.
By the way, same hardware: Vostro 1400, nVidia 8400 GS, Ubuntu Hardy, exactly same behavior.
With regards to #3, this can be partially fixed by disabling a gconf key. In particular, /apps/gnome- power-manager/ backlight/ enable ... Disble this and AC unplug is fixed, but brightness key still has same affect.
By the way, same hardware: Vostro 1400, nVidia 8400 GS, Ubuntu Hardy, exactly same behavior.