It does not specifically require them, although I guess you can use any one of the polyfills. You can also use oldschool JS syntax as well as others
But the better question would perhaps be, is mobservable really worth the decoupling from Meteor (if that’s your thing, by all means go for it) whereas we already have minimongo and Tracker which do the same thing with much more familiar and isomorphic API’s.
And as long as @mitar’s server-side work ends up in the core I’d say it beats mobservable front and back.
But of course, as always I’d like to ping one more maestro (in addition to those you’ve already did ping) @SkinnyGeek1010 to enlighten us 