How to roll back the fixes:
If you applied the Registry Key: follow the previous instructions to find the key you have created, select it, right-click and delete the key.
→ Remember: I can’t post it here 
If you used the audioengine.properties file: you don’t need to do anything, it is saved in the previos version’s preferences, and it still needs it.
Those who preferred to disable hyper-threading may want to re-enable it.
The MMCSS limitation exists of course, but the audio engine spawns threads in a very different way and should not affect Cubase. I say ‘should’ because on a limited amount of configurations issues may still be experienced. Way to long and complicated for a post, but if the issue kicks in, it is possible to improve, if not fix it completely. Those having MMCSS-related performance issues with Pro 10 should contact support.
The issue should be no more in the majority of cases, though - meaning undoing the fixes were needed is the only thing one needs to do.
[Edited]