Matthew Ferrin While I certainly still have my opinion about CSS-in-JS, I really recommend not doing inline-styles. There is a reason why they were banned from the HTML5 spec entirely.
Also, there is Vanilla CSS, which means you do your styling without any library or framework at all. Whenever you need to do simple things, don't use a library and try to workaround it when it doesn't fit 😉
Thank you for your write-up. Just some questions:
.login button[type="submit"] { background: blue; }