I'm not sold that this will provide any user-measurable increase in performance. If you are sold by some personal app benchmark, there is a good chance you are writing too much client side JS. And what is to say of other dependencies like jQuery, Bootstrap, Knockout, Angular, etc that do NOT use fast.js under the hood? It seems that the only real "win" I get is a fast "map" command, which, IFAIK, has NEVER been the problem of writing good software.

Now, if fast.js made sure we had the correct requirements, no distractions, clear milestones, and a dedicated team with no turn over, I'd import it in a second.