Great addon! It has made me happy for years. But now I have to migrate all my styles to Tampermonkey scripts due to the following reasons:
1. Firefox (both Windows and Android) cannot work normally with userstyles.org: lags all the time, almost impossible to edit styles on this web-site. These problems last for more than a month and I'm tired fighting them.
2. This addon works only partially in new Firefox for Android and Firefox Nightly: it applies styles well, but cannot edit them locally and cannot update them with new version from userstyles.org.

I will keep an eye on it. Maybe I'll be back later :)