I wrote a little hack for the nvidia_bl kernel module. I had the 127 brightness levels problem that resulted in the screen being too dark. I have a G105M on a Dell Inspiron 1370. I believe there is a problem with the way the register is handled in the code. The hack bloats up the min and max values for this register. A patch is attached, some explanation is at my blog
under "Backlight Fix". This fixes the darkness issue for me and gives me full control over just about the full range of brightness levels. Somebody might find this helpful.