Tracking scrolling issues (jank) down is not easily done and in that case the API "seems" that it might actually help you quantify the performance gains/losses from making the scrolling experience smoother across your user base (just an example). Still, it seems a pretty low level API cause it's not going to point you to the culprit component when problems arise rather it's just reporting on how you are doing fps-wise.
>How beneficial this would be to improving our ability to research user performance.
In the case of rendering at wikipedia-like-projects...well, I do not see it will have much effect, our main rendering case is real simple: text (in big amounts)+pictures (in small amounts). Then (correct me if I am wrong) our performance issues for readers probably come mostly from page load/image resolution/image downloads and none of these affect the frame rate.