There are so many websites (and in particular, web applications) where the vendor got a minor thing wrong. With Stylus and a bit of quality time with the Firefox Inspector, many of those issues can be easily papered over. And that's more than cosmetics: a password vault that uses fonts that mix up small L and digit one is a hazard, and an application where a tighter linespacing removes an unnecessary nested scrollbar becomes just a bit more productive. In short, Stylus is ideal whenever you can't just edit the CSS behind an application.

This is great for customizing my read experience on many, including company-internal websites, where I don't like their styling.

Nice

Очень хорошее расширение. Любой сайт с ним преображается.

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.

Does what it says. Great!