If you ever try to connect a Windows host to an Apple display you will most probably have a brightness problem. Despite the amount of time you spend fiddling with your graphics card settings, you will realise soon enough that the screen stays quite dark.
The problem is not with the brightness of the colours being displayed but with the back-light illumination within the display. The Brightness Controller utility will "speak" to the screen and allow you to adjust the back-light brightness to your liking.
Note: I am currently using it with Windows 8.1 and it works fine!
Currently supported displays:
27" Apple Thunderbolt Display
27" Apple LED Cinema Display
24" Apple LED Cinema Display
23" Apple Cinema Display HD (Acrylic frame)
20" Apple Cinema Display (Aluminum frame)
20" Apple Cinema Display (Acrylic frame)
In order to adjust this you will have to download this very useful utility called "Brightness Controller" from this website: http://www.holstschumacher.dk/p/brightness-controller.html
Download version 1.4.4 (Feb/2013)