physical Keyboard backlight question

I believe the update tied the keyboard backlight to the screen auto-backlight level. If you have that enabled, try turning it off. Might make it stay on for longer stretches instead of constantly adjusting. Also, make sure you aren't partially covering the light sensor as you type.

 

It's about 1cm to the right of the speaker on the face of the phone. If you cover it with your finger, you'll see the screen dim.