I've not used Stylish, but from looking their Chrome Extension page it looks like they don't allow you to write CSS for pages, but rather apply themes that have

I've not used Stylish, but from looking their Chrome Extension page it looks like they don't allow you to write CSS for pages, but rather apply themes that have been built for sites by third parties? Stylebot lets me just write css, or can grab an element off the page and they give you a GUI to edit the most common style properties. The ability to just write CSS as simple as .stupid-ad { display: none; } is what I was after.