Comparing the system state (i.e. registry values) after the 30-day grace period ran out to the system state after activating the system and to the system state of a backup shortly before the end of the grace period, it seems nothing important changes with regards to security, energy or performance settings.
The only things that happen are:
- a different desktop theme is activated every hour (black background with Windows version; changing the theme also sets OEMBackground=0 if no appropriate group policy is set)
- Windows updates are deactivated other than some important ones
- popup messages start to appear frequently, stating that the copy might not be genuine and should be activated
I also read that there is a pause during system start and that the small Windows programs no longer work / can no longer be downloaded, but I could not verify either of this.