I was experimenting with widget that would show information based on location. I noticed that it's currently not possible to keep display backlight turned on all the time. However, there is something you can do :
1. Disable 'Auto keylock' from phone settings
Example how to use sysinfo.lighton can be found here
Thing is, if 'Auto keylock' is enabled, controlling display light with sysinfo.lighton will only cause white screen.
I'm really hoping, that Nokia would fix this issue and offer better solution to keep light on.