I had Windows 8.0 on my laptop, and went to Win 8.1 earlier this year. Everything went well. Even this spring, when I installed the 8.1 update, things went well on my laptop. This was my test environment, as most days I work on my desktop. I decided to then update my desktop, and things went well overall, until I went to use SQL Server.
At first, I couldn’t connect to SQL Server from SSMS. No big deal, I thought the update had stopped a service. I checked Services, and was surprised to not see a SQL Server database service. I had a browser and VSS service, but nothing else.
I rebooted my machine, which didn’t help. I manually ran sqlservr.exe, and it failed with permissions issued. I tried repairing the SQL install, but that didn’t work either. More than a few people reported similar things, but nothing I found on the Internet worked. I kept getting security SPID errors, so I just uninstalled, and then reinstalled SQL Server.
I’m not sure under which accounts I had my service running, and it’s possible I used my own account, but usually I set up a SQLService account on my machines. In any case, it was a hassle and pain.
I’m not telling you to avoid the 8.1 Update, but I am warning you and noting that you might want to be sure you have good backups of your systems.