[lomnakkus]

The date/time cross-platformness is a big deal for business-type applications, at the very least. You tend to transfer/use a lot of dates/timestamps/what-have-you in that type of application. (This is a constant source of pain for me in scala.js.)

[gavinking]

ceylon.locale is also shaping up to be really useful. Localization in JS is just terrible.

[lomnakkus]

Yes, that's another of my pet peeves with scala.js since it basically splits your world into two around formatting of dates/time/currency/etc. (Things may have changed recently, but it was sorely lacking up until a few months ago.)