If your looking for es5 promises are much easier to polyfill and much more competitive than generators

It's actually how babel's "standard" async/await support works. First to generators, then generators to ES5-compatible code using Facebook's Regenerator (which includes a polyfill).

Pragmatic and it works, but the code isn't pretty. Which is why Kneden was made.

It is, the resulting code is just a bit harder to read, and the babel-polyfill is required. It's quite good considering they're transpiling generators actually, but it's hard to beat something working on a higher level (async/await straight to promises, like Kneden does.)