The funniest problem I ran into is that in Babel 6 using `typeof` does not work. Had to rewrite all our code to use Lodash type helpers because it is an external dependency and doesn't go through our build stack. We need our shit to work in production and don't have time to wait for forever.

Bug hasn't been fixed in almost a month: https://phabricator.babeljs.io/T6644

You'd think something like a basic language feature wouldn't break when you update your compiler. I did. I was wrong.

Thank the gods of software gardening that we were only using typeof in five or so places.

It's kinda funny actually. I remember the oft quoted maxim regarding very mature static languages: "It's never the compilers fault". This was obviously a hyperbole, but it held true most of the time. These days, the definition of "compiler" has gotten extremely loose on the web side, and it seems like correctness has gone by the wayside.

That's always been the case with fast-growing technologies. I remember finding a disturbing number of bugs in Java 1.3 c. 2000; if you ask Swift programmers today about the stability of the compiler, they could tell you all about compiler crashes & bugs.

If you want stability, use a technology that was popular 10 years ago. If you want to work on the bleeding edge, you will be bleeding. Decide what's appropriate for your project. The reason people worked in Java in 2000 or Swift/Babel today is so they can take advantage of temporary market opportunities where other people get deterred by the pain of capitalizing on them. This can be very financially lucrative if you yourself are willing to put up with that pain.