I'm sticking with 8 for now, I have tried upgrading to 8.1 three times now and every time I restart the system after install I get the error message "System_Service_Exception" and the system just keeps restarting and I have to use safe mode just to get into Windows, I have tried disabling all non windows programs including antivirus in msconfig and still get the error, I tried upgrading from a fresh Windows 8 install without any additional programs like antivirus installed only Windows 8 compatible chipset and LAN drivers to get internet access and still get the same error.
It would be helpful if it gave more information in the error message as to the cause, the only thing I can think is causing the issue is the chipset and LAN drivers as they are they are the only things I installed but they are the latest versions and obviously need to be installed so there's nothing I can do about that.
I would grab a Win8.1 RTM ISO(can do a MD5 check to make sure its a legit ISO) and do a clean install use the default Win8.1 install key(plenty of places on the net that list these via Google) then change the key after installation to your legit key ,that's what I did with one of my PCs.