Very convenient. Somehow it took me months to figure out how to make a style apply only to the current url (click the url parts in the small popup that opens when clicking the extension). I think the UI could be simplified to make it more user friendly, but overall it's quite good.
Some of my use cases :
- add `body{background:red} ` on your production website to not confuse it with staging.
- hide the advertising line at the top of the mailbox in yandex mail
- make a touch typing website responsive and ad free

I already have an ad blocker but this lets me get that ads space back for content.