I decided to jump in headfirst and upgrade my personal laptop to Windows 10 on release day. The upgrade process was really straight forward and I didn't encounter any problems. After about 90 minutes of downloading and updating, the system rebooted for the 2nd or 3rd time. I saw the Windows logon screen flash for a second, then it went blank.
The system appeared to be functioning; it was making sound, the numlock light went on and off, etc. but there was nothing visible on the display. I tried restarting several times and each time saw the same quick flash of the Windows login screen followed by a blank screen.
My first thought was that there was an issue with the video card driver (AMD FirePro M5950), so I attached an external monitor. If the video driver was a problem then the external display probably wouldn't work either. I was pleasantly surprised when the video popped up on the external display.
After fruitless searches of the internet and several rounds of upgrading and downgrading video drivers did not resolve the issue, I was preparing to roll back to Windows 7. I decided to check the BIOS to confirm the computer's specs so I could report the problem as part of the downgrade process.
Once in the BIOS, I noticed that the laptop's ambient light sensor was enabled. If working properly, this should help adjust the backlight level based on the lighting in the room. However it occurred to me that if it wasn't working correctly, it could potentially shut the display's backlight off. Figuring there was no harm, I disabled the sensor and rebooted one last time.
Bingo! Windows logon screen showed and it didn't go blank.
After a couple hours of using the newly upgraded machine, the display still seems to be working nicely. The ambient light sensor worked under Windows 7 immediately before the upgrade, so I suspect there is not yet full driver support for this particular device in Windows 10.
I figured I'd post this here in hopes it helps someone else who is encountering similar issues.