Which browsers, if any, support Object.observe ? I'm surprised I'm unable to find any info on this.

(And are you aware about any estimated times of arrival for this feature?)

About Object.observe: "Object.observe allows for the direct observation of changes to ECMAScript objects. It allows an observer to receive a time-ordered sequence of change records which describe the set of changes which took place to the set of observed objects." — see ecmascript.org, the Solution section.)

Edit November 2015: Apparently Object.observe has been cancelled:

http://www.infoq.com/news/2015/11/object-observe-withdrawn

https://esdiscuss.org/topic/an-update-on-object-observe

"I plan to withdraw the Object.observe proposal from TC39"

https://esdiscuss.org/topic/save-object-observe-please-make-weakmap-weakset-observable

"Save Object.observe()! (please)"