Running unit tests in non-Chrome browsers raised some doubts about this API which is currently used in the Date and Currency pipes.

To start with, it is not supported in all Safari versions (desktop and mobile) and older browsers:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl
http://caniuse.com/#search=intl

Then, on browsers which support it, the result doesn't match what Chrome does.
On Firefox, one of the test fires this 2 years old bug: https://bugzilla.mozilla.org/show_bug.cgi?id=866372
On IE11, most tests are failing due to discrepancies in output (formatting, white space, special chars,etc).

At the end of the day, it seems only reliable in Chrome, but it is also difficult to polyfill.
So, if anyone has a good solution to that, please speak up!