* uninstall and re-install all your applications (backup application data if required)
* microG lacks features
* if you use AppOps, PrivacyGuard or the like you have to grant microG GmsCore **all** permissions, if you prevent some permissions, some apps or features might not work as expected or not at all. Note: some APIs/features are stubs in microG GmsCore, meaning they exist that apps don't complain, but they do nothing - thus blocking microG GmsCore is pretty much of no benefit.
* ROM lags after applying signature spoofing patch
* some ROMs already have the patch built-in, if you patch those ROMs (again), it results in heavy lags