trackpad work. You need to install trackpad++
(http://www.techspot.com/downloads/4967-trackpad-control-module.html), it will enable the trackpad driver on boot camp. After you install the trackpad++, trackpad++ will complain something. ingnore it. You should be able to enable trackpad. And you can now even uninstall the trackpad++, the trackpad will sill work.
Also, went into Device Manager and on the two "Touchpad" entries with the bang on them, went to "Update Driver" -> "Browse My Computer" -> "Let me pick from a list..." and changed them both to USB Input Device. Reboot.Go back to Device Manager, do an "Update Driver" again, let it search automatically, and one comes back as Apple Multitouch and the other as Apple Multitouch Mouse. Rebooted again, trackpad working and shows up in Boot Camp control panel.
brightness, what graphics card are you using? It might be due to the auto adjusting brightness running there. You can go to your power options, edit the one you are using (Change plan settings >> Change advanced power settings) and look for Batteries >> Enable adaptive brightness and disable the one you are using. After that, the scrollbar for adjusting brightness in power options should work again.
Tried your suggestion about brightness, ie, turning off the 'enable adaptive brightness'. But no change. The control in the Charms bar is stiff unavailable. Rebooted after doing the change as well to make sure.
I can only change the screen brightness by going into OSX and making the changes there. It then seems to keep this setting for when i boot into Windows 8. Just don;t seem to be able to make the change within Windows 8 itself.