Yeah, I'm actually completely wrong. My apologies to the Buble team. For whatever reason, I thought I saw an announcement of Buble essentially saying it was an opinionated feature-freeze of Babel with most of the configuration stripped out, but it appears to be a totally new project.
That said, the two are very different tools. Buble appears to be essentially string manipulation (which Babel does to occasionally with babel-template) built on top of Acorn. It's much simpler but there are a lot of useful transformations you simply can't do with that approach.
Edit: After some further looking into the project, I have to say that it seems like it would nice & easy to use for simple transformations, like the aforementioned React.createClass -> class Foo extends React.Component. However, you have to keep in mind that code that is not spec-compliant will break in mysterious ways perhaps months or years into the future. It may not be worth it, despite the ease.
`yarn install babel-cli babel-preset-es2015; ./node_modules/.bin/babel --presets es2015 <sources> -d <out-dir>` is not particularly difficult.
> will break in mysterious ways perhaps months or years into the future
Since you already recognized you know nothing about Buble can you please stop making absurd claims about THINGS YOU DON'T KNOW?
What are specs, by the way? I don't care if Buble isn't following stupid specs. Browser vendors will change these specs a million times, Babel will follow up with new versions with a thousand breaking changes and require you to install a ton of packages, clean old packages, erase your hard disk and kill your neighbours. Buble will just keep working.