> Phew! A component just for a button. What a twist! I don't think most people are making components for each html element. In fact, I'd say this is pretty redundant and overengineering things in a bad way. Guess what - html has these nifty components called buttons too, and you can also style them. Wouldn't any minor change to your button component require then passing in props (just like classes)? <Button propName={"danger"}><button></button></Button> doesn't really seem better than <button class="btn--danger"></button> to me.

We use custom components like this at work, and it actually works quite nicely because you get to see all the different "types" of buttons at a glance by looking at the prop types. Using the component looks something like this:

<Button label="Click me!" primary />

I've found that it's helpful for enforcing consistency, so that you have to go out of your way to apply custom styles to a button (which isn't required 95% of the time). Plus, it helps abstract things that don't have anything to do with the <button> HTML element but are often tied together, like being able to automatically make a button a link without having to wrap it in an <a> tag:

<Button label="Home" href="/" />

It's all minor stuff, but it enforces consistency and keeps you from having to think about CSS classes at all most of the time.